diff mbox series

[v2,2/2] attr: add flag `-r|--revisions` to work with revisions

Message ID 20221209210321.709156-3-karthik.188@gmail.com (mailing list archive)
State Superseded
Headers show
Series check-attr: add support to work with revisions | expand

Commit Message

Karthik Nayak Dec. 9, 2022, 9:03 p.m. UTC
Git check-attr currently doesn't check the git worktree, it either
checks the index or the files directly. This means we cannot check the
attributes for a file against a certain revision.

Add a new flag `--revision`/`-r` which will allow it work with
revisions. This command will now, instead of checking the files/index,
try and receive the blob for the given attribute file against the
provided revision. The flag overrides checking against the index and
filesystem and also works with bare repositories.

We cannot use the `<rev>:<path>` syntax like the one used in `git show`
because any non-flag parameter before `--` is treated as an attribute
and any parameter after `--` is treated as a pathname.

This involves creating a new function `read_attr_from_blob`, which given
the path reads the blob for the path against the provided revision and
parses the attributes line by line. This function is plugged into
`read_attr()` function wherein we go through the different attributes.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Co-authored-by: toon@iotcl.com
---
 Documentation/git-check-attr.txt |   8 ++-
 archive.c                        |   2 +-
 attr.c                           | 100 ++++++++++++++++++++++---------
 attr.h                           |   7 ++-
 builtin/check-attr.c             |  33 ++++++----
 builtin/pack-objects.c           |   2 +-
 convert.c                        |   2 +-
 ll-merge.c                       |   4 +-
 pathspec.c                       |   2 +-
 t/t0003-attributes.sh            |  64 +++++++++++++++++++-
 userdiff.c                       |   2 +-
 ws.c                             |   2 +-
 12 files changed, 175 insertions(+), 53 deletions(-)

Comments

Phillip Wood Dec. 13, 2022, 3:18 p.m. UTC | #1
Hi Karthik

I've got a couple of comments below about the details of the 
implementation but the basic idea seems reasonable.

On 09/12/2022 21:03, Karthik Nayak wrote:
> Git check-attr currently doesn't check the git worktree,

Normally worktree refers to the directory on disk where the repository's 
working copy is checked out. Here you seem to mean something else.

> it either
> checks the index or the files directly. This means we cannot check the
> attributes for a file against a certain revision.
> 
> Add a new flag `--revision`/`-r` which will allow it work with
> revisions. This command will now, instead of checking the files/index,
> try and receive the blob for the given attribute file against the
> provided revision. The flag overrides checking against the index and
> filesystem and also works with bare repositories.

The system, global and the attributes in .git/info/attributes from the 
filesystem are still used. It would be useful to document that and 
explain in the commit message why that is useful when using -r.

-r is documented as accepting a revision but actually accepts any tree. 
That means a user can pass "-r HEAD:subdirectory" and all the attributes 
will be looked up as if subdirectory was the root directory of the 
repository which might be confusing. It would be helpful to know if 
passing a tree rather than a revision is useful. If it isn't then you 
could use lookup_commit_reference() to ensure the user passes a revision.

Best Wishes

Phillip

> We cannot use the `<rev>:<path>` syntax like the one used in `git show`
> because any non-flag parameter before `--` is treated as an attribute
> and any parameter after `--` is treated as a pathname.
> 
> This involves creating a new function `read_attr_from_blob`, which given
> the path reads the blob for the path against the provided revision and
> parses the attributes line by line. This function is plugged into
> `read_attr()` function wherein we go through the different attributes.
> 
> Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
> Co-authored-by: toon@iotcl.com
> ---
>   Documentation/git-check-attr.txt |   8 ++-
>   archive.c                        |   2 +-
>   attr.c                           | 100 ++++++++++++++++++++++---------
>   attr.h                           |   7 ++-
>   builtin/check-attr.c             |  33 ++++++----
>   builtin/pack-objects.c           |   2 +-
>   convert.c                        |   2 +-
>   ll-merge.c                       |   4 +-
>   pathspec.c                       |   2 +-
>   t/t0003-attributes.sh            |  64 +++++++++++++++++++-
>   userdiff.c                       |   2 +-
>   ws.c                             |   2 +-
>   12 files changed, 175 insertions(+), 53 deletions(-)
> 
> diff --git a/Documentation/git-check-attr.txt b/Documentation/git-check-attr.txt
> index 84f41a8e82..3dc61f0fdc 100644
> --- a/Documentation/git-check-attr.txt
> +++ b/Documentation/git-check-attr.txt
> @@ -9,8 +9,8 @@ git-check-attr - Display gitattributes information
>   SYNOPSIS
>   --------
>   [verse]
> -'git check-attr' [-a | --all | <attr>...] [--] <pathname>...
> -'git check-attr' --stdin [-z] [-a | --all | <attr>...]
> +'git check-attr' [-a | --all | <attr>...] [-r <revision>] [--] <pathname>...
> +'git check-attr' --stdin [-z] [-a | --all | <attr>...] [-r <revision>]
>   
>   DESCRIPTION
>   -----------
> @@ -36,6 +36,10 @@ OPTIONS
>   	If `--stdin` is also given, input paths are separated
>   	with a NUL character instead of a linefeed character.
>   
> +--r <revision>::
> +--revision=<revision>::
> +	Check attributes against the specified revision.
> +
>   \--::
>   	Interpret all preceding arguments as attributes and all following
>   	arguments as path names.
> diff --git a/archive.c b/archive.c
> index 941495f5d7..81ff76fce9 100644
> --- a/archive.c
> +++ b/archive.c
> @@ -120,7 +120,7 @@ static const struct attr_check *get_archive_attrs(struct index_state *istate,
>   	static struct attr_check *check;
>   	if (!check)
>   		check = attr_check_initl("export-ignore", "export-subst", NULL);
> -	git_check_attr(istate, path, check);
> +	git_check_attr(istate, NULL, path, check);
>   	return check;
>   }
>   
> diff --git a/attr.c b/attr.c
> index 42ad6de8c7..99883024ec 100644
> --- a/attr.c
> +++ b/attr.c
> @@ -11,8 +11,13 @@
>   #include "exec-cmd.h"
>   #include "attr.h"
>   #include "dir.h"
> +#include "git-compat-util.h"
> +#include "strbuf.h"
> +#include "tree-walk.h"
>   #include "utf8.h"
>   #include "quote.h"
> +#include "revision.h"
> +#include "object-store.h"
>   #include "thread-utils.h"
>   
>   const char git_attr__true[] = "(builtin)true";
> @@ -729,14 +734,62 @@ static struct attr_stack *read_attr_from_file(const char *path, unsigned flags)
>   	return res;
>   }
>   
> -static struct attr_stack *read_attr_from_index(struct index_state *istate,
> -					       const char *path,
> -					       unsigned flags)
> +static struct attr_stack *read_attr_from_buf(char *buf, const char *path,
> +					     unsigned flags)
>   {
>   	struct attr_stack *res;
> -	char *buf, *sp;
> +	char *sp;
>   	int lineno = 0;
>   
> +	if (!buf)
> +		return NULL;
> +
> +	CALLOC_ARRAY(res, 1);
> +	for (sp = buf; *sp;) {
> +		char *ep;
> +		int more;
> +
> +		ep = strchrnul(sp, '\n');
> +		more = (*ep == '\n');
> +		*ep = '\0';
> +		handle_attr_line(res, sp, path, ++lineno, flags);
> +		sp = ep + more;
> +	}
> +	free(buf);
> +
> +	return res;
> +}
> +
> +static struct attr_stack *read_attr_from_blob(struct index_state *istate,
> +					      const struct object_id *tree_oid,
> +					      const char *path, unsigned flags)
> +{
> +	struct object_id oid;
> +	unsigned long sz;
> +	enum object_type type;
> +	void *buf;
> +	unsigned short mode;
> +
> +	if (!tree_oid)
> +		return NULL;
> +
> +	if (get_tree_entry(istate->repo, tree_oid, path, &oid, &mode))
> +		return NULL;
> +
> +	buf = read_object_file(&oid, &type, &sz);
> +	if (!buf || type != OBJ_BLOB) {
> +		free(buf);
> +		return NULL;
> +	}
> +
> +	return read_attr_from_buf(buf, path, flags);
> +}
> +
> +static struct attr_stack *read_attr_from_index(struct index_state *istate,
> +					       const char *path, unsigned flags)
> +{
> +	char *buf;
> +
>   	if (!istate)
>   		return NULL;
>   
> @@ -758,28 +811,19 @@ static struct attr_stack *read_attr_from_index(struct index_state *istate,
>   	if (!buf)
>   		return NULL;
>   
> -	CALLOC_ARRAY(res, 1);
> -	for (sp = buf; *sp; ) {
> -		char *ep;
> -		int more;
> -
> -		ep = strchrnul(sp, '\n');
> -		more = (*ep == '\n');
> -		*ep = '\0';
> -		handle_attr_line(res, sp, path, ++lineno, flags);
> -		sp = ep + more;
> -	}
> -	free(buf);
> -	return res;
> +	return read_attr_from_buf(buf, path, flags);
>   }
>   
>   static struct attr_stack *read_attr(struct index_state *istate,
> +				    const struct object_id *tree_oid,
>   				    const char *path, unsigned flags)
>   {
>   	struct attr_stack *res = NULL;
>   
>   	if (direction == GIT_ATTR_INDEX) {
>   		res = read_attr_from_index(istate, path, flags);
> +	} else if (tree_oid) {
> +		res = read_attr_from_blob(istate, tree_oid, path, flags);
>   	} else if (!is_bare_repository()) {
>   		if (direction == GIT_ATTR_CHECKOUT) {
>   			res = read_attr_from_index(istate, path, flags);
> @@ -839,6 +883,7 @@ static void push_stack(struct attr_stack **attr_stack_p,
>   }
>   
>   static void bootstrap_attr_stack(struct index_state *istate,
> +				 const struct object_id *tree_oid,
>   				 struct attr_stack **stack)
>   {
>   	struct attr_stack *e;
> @@ -864,7 +909,7 @@ static void bootstrap_attr_stack(struct index_state *istate,
>   	}
>   
>   	/* root directory */
> -	e = read_attr(istate, GITATTRIBUTES_FILE, flags | READ_ATTR_NOFOLLOW);
> +	e = read_attr(istate, tree_oid, GITATTRIBUTES_FILE, flags | READ_ATTR_NOFOLLOW);
>   	push_stack(stack, e, xstrdup(""), 0);
>   
>   	/* info frame */
> @@ -878,6 +923,7 @@ static void bootstrap_attr_stack(struct index_state *istate,
>   }
>   
>   static void prepare_attr_stack(struct index_state *istate,
> +			       const struct object_id *tree_oid,
>   			       const char *path, int dirlen,
>   			       struct attr_stack **stack)
>   {
> @@ -899,7 +945,7 @@ static void prepare_attr_stack(struct index_state *istate,
>   	 * .gitattributes in deeper directories to shallower ones,
>   	 * and finally use the built-in set as the default.
>   	 */
> -	bootstrap_attr_stack(istate, stack);
> +	bootstrap_attr_stack(istate, tree_oid, stack);
>   
>   	/*
>   	 * Pop the "info" one that is always at the top of the stack.
> @@ -954,7 +1000,7 @@ static void prepare_attr_stack(struct index_state *istate,
>   		strbuf_add(&pathbuf, path + pathbuf.len, (len - pathbuf.len));
>   		strbuf_addf(&pathbuf, "/%s", GITATTRIBUTES_FILE);
>   
> -		next = read_attr(istate, pathbuf.buf, READ_ATTR_NOFOLLOW);
> +		next = read_attr(istate, tree_oid, pathbuf.buf, READ_ATTR_NOFOLLOW);
>   
>   		/* reset the pathbuf to not include "/.gitattributes" */
>   		strbuf_setlen(&pathbuf, len);
> @@ -1074,8 +1120,8 @@ static void determine_macros(struct all_attrs_item *all_attrs,
>    * Otherwise all attributes are collected.
>    */
>   static void collect_some_attrs(struct index_state *istate,
> -			       const char *path,
> -			       struct attr_check *check)
> +			       const struct object_id *tree_oid,
> +			       const char *path, struct attr_check *check)
>   {
>   	int pathlen, rem, dirlen;
>   	const char *cp, *last_slash = NULL;
> @@ -1094,7 +1140,7 @@ static void collect_some_attrs(struct index_state *istate,
>   		dirlen = 0;
>   	}
>   
> -	prepare_attr_stack(istate, path, dirlen, &check->stack);
> +	prepare_attr_stack(istate, tree_oid, path, dirlen, &check->stack);
>   	all_attrs_init(&g_attr_hashmap, check);
>   	determine_macros(check->all_attrs, check->stack);
>   
> @@ -1103,12 +1149,12 @@ static void collect_some_attrs(struct index_state *istate,
>   }
>   
>   void git_check_attr(struct index_state *istate,
> -		    const char *path,
> +		    const struct object_id *tree_oid, const char *path,
>   		    struct attr_check *check)
>   {
>   	int i;
>   
> -	collect_some_attrs(istate, path, check);
> +	collect_some_attrs(istate, tree_oid, path, check);
>   
>   	for (i = 0; i < check->nr; i++) {
>   		size_t n = check->items[i].attr->attr_nr;
> @@ -1119,13 +1165,13 @@ void git_check_attr(struct index_state *istate,
>   	}
>   }
>   
> -void git_all_attrs(struct index_state *istate,
> +void git_all_attrs(struct index_state *istate, const struct object_id *tree_oid,
>   		   const char *path, struct attr_check *check)
>   {
>   	int i;
>   
>   	attr_check_reset(check);
> -	collect_some_attrs(istate, path, check);
> +	collect_some_attrs(istate, tree_oid, path, check);
>   
>   	for (i = 0; i < check->all_attrs_nr; i++) {
>   		const char *name = check->all_attrs[i].attr->name;
> diff --git a/attr.h b/attr.h
> index 3fb40cced0..f4a2bedd68 100644
> --- a/attr.h
> +++ b/attr.h
> @@ -1,6 +1,8 @@
>   #ifndef ATTR_H
>   #define ATTR_H
>   
> +#include "hash.h"
> +
>   /**
>    * gitattributes mechanism gives a uniform way to associate various attributes
>    * to set of paths.
> @@ -190,13 +192,14 @@ void attr_check_free(struct attr_check *check);
>   const char *git_attr_name(const struct git_attr *);
>   
>   void git_check_attr(struct index_state *istate,
> -		    const char *path, struct attr_check *check);
> +		    const struct object_id *tree_oid, const char *path,
> +		    struct attr_check *check);
>   
>   /*
>    * Retrieve all attributes that apply to the specified path.
>    * check holds the attributes and their values.
>    */
> -void git_all_attrs(struct index_state *istate,
> +void git_all_attrs(struct index_state *istate, const struct object_id *tree_oid,
>   		   const char *path, struct attr_check *check);
>   
>   enum git_attr_direction {
> diff --git a/builtin/check-attr.c b/builtin/check-attr.c
> index 0fef10eb6b..28da31c2a5 100644
> --- a/builtin/check-attr.c
> +++ b/builtin/check-attr.c
> @@ -1,3 +1,4 @@
> +#include "repository.h"
>   #define USE_THE_INDEX_VARIABLE
>   #include "builtin.h"
>   #include "cache.h"
> @@ -9,9 +10,10 @@
>   static int all_attrs;
>   static int cached_attrs;
>   static int stdin_paths;
> +static char *revision;
>   static const char * const check_attr_usage[] = {
> -N_("git check-attr [-a | --all | <attr>...] [--] <pathname>..."),
> -N_("git check-attr --stdin [-z] [-a | --all | <attr>...]"),
> +N_("git check-attr [-a | --all | <attr>...] [-r <revision>] [--] <pathname>..."),
> +N_("git check-attr --stdin [-z] [-a | --all | <attr>...] [-r <revision>]"),
>   NULL
>   };
>   
> @@ -23,6 +25,7 @@ static const struct option check_attr_options[] = {
>   	OPT_BOOL(0 , "stdin", &stdin_paths, N_("read file names from stdin")),
>   	OPT_BOOL('z', NULL, &nul_term_line,
>   		 N_("terminate input and output records by a NUL character")),
> +	OPT_STRING('r', "revision", &revision, N_("revision"), N_("check attributes at this revision")),
>   	OPT_END()
>   };
>   
> @@ -55,27 +58,26 @@ static void output_attr(struct attr_check *check, const char *file)
>   	}
>   }
>   
> -static void check_attr(const char *prefix,
> -		       struct attr_check *check,
> -		       int collect_all,
> +static void check_attr(const char *prefix, struct attr_check *check,
> +		       const struct object_id *tree_oid, int collect_all,
>   		       const char *file)
> +
>   {
>   	char *full_path =
>   		prefix_path(prefix, prefix ? strlen(prefix) : 0, file);
>   
>   	if (collect_all) {
> -		git_all_attrs(&the_index, full_path, check);
> +		git_all_attrs(&the_index, tree_oid, full_path, check);
>   	} else {
> -		git_check_attr(&the_index, full_path, check);
> +		git_check_attr(&the_index, tree_oid, full_path, check);
>   	}
>   	output_attr(check, file);
>   
>   	free(full_path);
>   }
>   
> -static void check_attr_stdin_paths(const char *prefix,
> -				   struct attr_check *check,
> -				   int collect_all)
> +static void check_attr_stdin_paths(const char *prefix, struct attr_check *check,
> +				   const struct object_id *tree_oid, int collect_all)
>   {
>   	struct strbuf buf = STRBUF_INIT;
>   	struct strbuf unquoted = STRBUF_INIT;
> @@ -89,7 +91,7 @@ static void check_attr_stdin_paths(const char *prefix,
>   				die("line is badly quoted");
>   			strbuf_swap(&buf, &unquoted);
>   		}
> -		check_attr(prefix, check, collect_all, buf.buf);
> +		check_attr(prefix, check, tree_oid, collect_all, buf.buf);
>   		maybe_flush_or_die(stdout, "attribute to stdout");
>   	}
>   	strbuf_release(&buf);
> @@ -105,6 +107,7 @@ static NORETURN void error_with_usage(const char *msg)
>   int cmd_check_attr(int argc, const char **argv, const char *prefix)
>   {
>   	struct attr_check *check;
> +	struct object_id tree_oid;
>   	int cnt, i, doubledash, filei;
>   
>   	if (!is_bare_repository())
> @@ -176,11 +179,15 @@ int cmd_check_attr(int argc, const char **argv, const char *prefix)
>   		}
>   	}
>   
> +	if (revision)
> +		if (repo_get_oid_tree(the_repository, revision, &tree_oid))
> +			error("%s: not a valid revision", revision);
> +
>   	if (stdin_paths)
> -		check_attr_stdin_paths(prefix, check, all_attrs);
> +		check_attr_stdin_paths(prefix, check, &tree_oid, all_attrs);
>   	else {
>   		for (i = filei; i < argc; i++)
> -			check_attr(prefix, check, all_attrs, argv[i]);
> +			check_attr(prefix, check, &tree_oid, all_attrs, argv[i]);
>   		maybe_flush_or_die(stdout, "attribute to stdout");
>   	}
>   
> diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
> index 573d0b20b7..89535cfa6a 100644
> --- a/builtin/pack-objects.c
> +++ b/builtin/pack-objects.c
> @@ -1318,7 +1318,7 @@ static int no_try_delta(const char *path)
>   
>   	if (!check)
>   		check = attr_check_initl("delta", NULL);
> -	git_check_attr(the_repository->index, path, check);
> +	git_check_attr(the_repository->index, NULL, path, check);
>   	if (ATTR_FALSE(check->items[0].value))
>   		return 1;
>   	return 0;
> diff --git a/convert.c b/convert.c
> index 9b67649032..a54d1690c0 100644
> --- a/convert.c
> +++ b/convert.c
> @@ -1308,7 +1308,7 @@ void convert_attrs(struct index_state *istate,
>   		git_config(read_convert_config, NULL);
>   	}
>   
> -	git_check_attr(istate, path, check);
> +	git_check_attr(istate, NULL, path, check);
>   	ccheck = check->items;
>   	ca->crlf_action = git_path_check_crlf(ccheck + 4);
>   	if (ca->crlf_action == CRLF_UNDEFINED)
> diff --git a/ll-merge.c b/ll-merge.c
> index 22a603e8af..130d26501c 100644
> --- a/ll-merge.c
> +++ b/ll-merge.c
> @@ -391,7 +391,7 @@ enum ll_merge_result ll_merge(mmbuffer_t *result_buf,
>   		normalize_file(theirs, path, istate);
>   	}
>   
> -	git_check_attr(istate, path, check);
> +	git_check_attr(istate, NULL, path, check);
>   	ll_driver_name = check->items[0].value;
>   	if (check->items[1].value) {
>   		marker_size = atoi(check->items[1].value);
> @@ -419,7 +419,7 @@ int ll_merge_marker_size(struct index_state *istate, const char *path)
>   
>   	if (!check)
>   		check = attr_check_initl("conflict-marker-size", NULL);
> -	git_check_attr(istate, path, check);
> +	git_check_attr(istate, NULL, path, check);
>   	if (check->items[0].value) {
>   		marker_size = atoi(check->items[0].value);
>   		if (marker_size <= 0)
> diff --git a/pathspec.c b/pathspec.c
> index 46e77a85fe..48dec2c709 100644
> --- a/pathspec.c
> +++ b/pathspec.c
> @@ -732,7 +732,7 @@ int match_pathspec_attrs(struct index_state *istate,
>   	if (name[namelen])
>   		name = to_free = xmemdupz(name, namelen);
>   
> -	git_check_attr(istate, name, item->attr_check);
> +	git_check_attr(istate, NULL, name, item->attr_check);
>   
>   	free(to_free);
>   
> diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh
> index b3aabb8aa3..042af0239f 100755
> --- a/t/t0003-attributes.sh
> +++ b/t/t0003-attributes.sh
> @@ -25,7 +25,14 @@ attr_check_quote () {
>   	git check-attr test -- "$path" >actual &&
>   	echo "\"$quoted_path\": test: $expect" >expect &&
>   	test_cmp expect actual
> +}
> +
> +attr_check_revision () {
> +	path="$1" expect="$2" revision="$3" git_opts="$4" &&
>   
> +	git $git_opts check-attr -r $revision test -- "$path" >actual 2>err &&
> +	echo "$path: test: $expect" >expect &&
> +	test_cmp expect actual
>   }
>   
>   test_expect_success 'open-quoted pathname' '
> @@ -33,7 +40,6 @@ test_expect_success 'open-quoted pathname' '
>   	attr_check a unspecified
>   '
>   
> -
>   test_expect_success 'setup' '
>   	mkdir -p a/b/d a/c b &&
>   	(
> @@ -80,12 +86,38 @@ test_expect_success 'setup' '
>   	EOF
>   '
>   
> +test_expect_success 'setup branches' '
> +	(
> +		echo "f	test=f" &&
> +		echo "a/i test=n"
> +	) | git hash-object -w --stdin >id &&
> +	git update-index --add --cacheinfo 100644,$(cat id),foo/bar/.gitattributes &&
> +	git write-tree >id &&
> +	tree_id=$(cat id) &&
> +	git commit-tree $tree_id -m "random commit message" >id &&
> +	commit_id=$(cat id) &&
> +	git update-ref refs/heads/branch1 $commit_id &&
> +
> +	(
> +		echo "g test=g" &&
> +		echo "a/i test=m"
> +	) | git hash-object -w --stdin >id &&
> +	git update-index --add --cacheinfo 100644,$(cat id),foo/bar/.gitattributes &&
> +	git write-tree >id &&
> +	tree_id=$(cat id) &&
> +	git commit-tree $tree_id -m "random commit message" >id &&
> +	commit_id=$(cat id) &&
> +	git update-ref refs/heads/branch2 $commit_id
> +'
> +
>   test_expect_success 'command line checks' '
>   	test_must_fail git check-attr &&
>   	test_must_fail git check-attr -- &&
>   	test_must_fail git check-attr test &&
>   	test_must_fail git check-attr test -- &&
>   	test_must_fail git check-attr -- f &&
> +	test_must_fail git check-attr -r &&
> +	test_must_fail git check-attr -r not-a-valid-ref &&
>   	echo "f" | test_must_fail git check-attr --stdin &&
>   	echo "f" | test_must_fail git check-attr --stdin -- f &&
>   	echo "f" | test_must_fail git check-attr --stdin test -- f &&
> @@ -287,6 +319,15 @@ test_expect_success 'using --git-dir and --work-tree' '
>   	)
>   '
>   
> +test_expect_success 'using --revision' '
> +	attr_check_revision foo/bar/f f branch1 &&
> +	attr_check_revision foo/bar/a/i n branch1 &&
> +	attr_check_revision foo/bar/f unspecified branch2 &&
> +	attr_check_revision foo/bar/a/i m branch2 &&
> +	attr_check_revision foo/bar/g g branch2 &&
> +	attr_check_revision foo/bar/g unspecified branch1
> +'
> +
>   test_expect_success 'setup bare' '
>   	git clone --template= --bare . bare.git
>   '
> @@ -306,6 +347,27 @@ test_expect_success 'bare repository: check that .gitattribute is ignored' '
>   	)
>   '
>   
> +test_expect_success 'bare repository: with --revision' '
> +	(
> +		cd bare.git &&
> +		(
> +			echo "f	test=f" &&
> +			echo "a/i test=a/i"
> +		) | git hash-object -w --stdin >id &&
> +		git update-index --add --cacheinfo 100644 $(cat id) .gitattributes &&
> +		git write-tree >id &&
> +		tree_id=$(cat id) &&
> +		git commit-tree $tree_id -m "random commit message" >id &&
> +		commit_id=$(cat id) &&
> +		git update-ref refs/heads/master $commit_id &&
> +		attr_check_revision f f HEAD &&
> +		attr_check_revision a/f f HEAD &&
> +		attr_check_revision a/c/f f HEAD &&
> +		attr_check_revision a/i a/i HEAD &&
> +		attr_check_revision subdir/a/i unspecified HEAD
> +	)
> +'
> +
>   test_expect_success 'bare repository: check that --cached honors index' '
>   	(
>   		cd bare.git &&
> diff --git a/userdiff.c b/userdiff.c
> index 151d9a5278..b66f090a0b 100644
> --- a/userdiff.c
> +++ b/userdiff.c
> @@ -412,7 +412,7 @@ struct userdiff_driver *userdiff_find_by_path(struct index_state *istate,
>   		check = attr_check_initl("diff", NULL);
>   	if (!path)
>   		return NULL;
> -	git_check_attr(istate, path, check);
> +	git_check_attr(istate, NULL, path, check);
>   
>   	if (ATTR_TRUE(check->items[0].value))
>   		return &driver_true;
> diff --git a/ws.c b/ws.c
> index 6e69877f25..eadbbe5667 100644
> --- a/ws.c
> +++ b/ws.c
> @@ -78,7 +78,7 @@ unsigned whitespace_rule(struct index_state *istate, const char *pathname)
>   	if (!attr_whitespace_rule)
>   		attr_whitespace_rule = attr_check_initl("whitespace", NULL);
>   
> -	git_check_attr(istate, pathname, attr_whitespace_rule);
> +	git_check_attr(istate, NULL, pathname, attr_whitespace_rule);
>   	value = attr_whitespace_rule->items[0].value;
>   	if (ATTR_TRUE(value)) {
>   		/* true (whitespace) */
Junio C Hamano Dec. 14, 2022, 1:28 a.m. UTC | #2
Phillip Wood <phillip.wood123@gmail.com> writes:

> I've got a couple of comments below about the details of the
> implementation but the basic idea seems reasonable.
>
> On 09/12/2022 21:03, Karthik Nayak wrote:
>> Git check-attr currently doesn't check the git worktree,
>
> Normally worktree refers to the directory on disk where the
> repository's working copy is checked out. Here you seem to mean
> something else.

Strictly speaking, what you just said is "working tree".  The term
"worktree" in Git's context yet means something slightly different.
You can arrange to have multiple working trees attached to a single
repository, and each of these is called a "worktree" attached to the
repository.

In any case, thanks for pointing out that the original's wording is
wrong.  It is natural to read it to claim that we do not check the
.gitattributes files that are checked out in the working trees,
which is utterly incorrect.

>> it either
>> checks the index or the files directly.

> This means we cannot check the
> attributes for a file against a certain revision.

Whenever one is tempted to say "This means", one should realize that
one does not have absolute confidence in whatever written before it,
in other words, without additional explanation, one suspects that
what one wanted to say would not be understood.

A good piece of advice for such a person is to try rewriting WITHOUT
anything before (and including) "This means".  And I think this is a
good example to which the advice applies well.

    There is no way with "git check-attr" to apply attributes from
    .gitattributes files recorded in the same treeish to paths in a
    treeish object.

Our usual preference is to (1) start by describing the current state
and (2) propose what can be done by deviating from it, in that
order, so one might write it like so:

    The contents of the .gitattributes files may evolve over time,
    but "git check-attr" always checks attributes against them in
    the working tree and/or in the index.  It may be beneficial to
    optionally allow the version of .gitattributes found in the same
    commit when checking the attributes for paths in an older commit.

By the way, applying the attributes from the working tree is by
design and it should stay to be the default.  People are almost
always working near the tip of the history, and working tree files
are by definition ahead of any committed version---it is a feature
that users can correct attribute definitions in their working tree
files and then apply them to paths in the committed version.

>> Add a new flag `--revision`/`-r` which will allow it work with
>> revisions. This command will now, instead of checking the files/index,
>> try and receive the blob for the given attribute file against the
>> provided revision. The flag overrides checking against the index and
>> filesystem and also works with bare repositories.
>
> The system, global and the attributes in .git/info/attributes from the
> filesystem are still used. It would be useful to document that and
> explain in the commit message why that is useful when using -r.
>
> -r is documented as accepting a revision but actually accepts any
>  tree. That means a user can pass "-r HEAD:subdirectory" and all the
>  attributes will be looked up as if subdirectory was the root
>  directory of the repository which might be confusing. It would be
>  helpful to know if passing a tree rather than a revision is
>  useful. If it isn't then you could use lookup_commit_reference() to
> ensure the user passes a revision.

Unless you use ancestry relationships in any way [*], you do not
want to require commits when an operation only requires trees.  In
this case, taking tree-ish and documenting it as such is the right
thing to do.

[Footnote]

* A good example that makes sense to limit to commit-ishes is when
  merging two histories (without requiring the user to supply the
  merge-base). You'd need to compute the merge-bases, so you require
  two committishes and it is not enough to take two trees.
Karthik Nayak Dec. 15, 2022, 8:20 p.m. UTC | #3
On Wed, Dec 14, 2022 at 2:28 AM Junio C Hamano <gitster@pobox.com> wrote:
>
> Phillip Wood <phillip.wood123@gmail.com> writes:
>
> > I've got a couple of comments below about the details of the
> > implementation but the basic idea seems reasonable.
> >
> > On 09/12/2022 21:03, Karthik Nayak wrote:
> >> Git check-attr currently doesn't check the git worktree,
> >
> > Normally worktree refers to the directory on disk where the
> > repository's working copy is checked out. Here you seem to mean
> > something else.
>
> Strictly speaking, what you just said is "working tree".  The term
> "worktree" in Git's context yet means something slightly different.
> You can arrange to have multiple working trees attached to a single
> repository, and each of these is called a "worktree" attached to the
> repository.
>
> In any case, thanks for pointing out that the original's wording is
> wrong.  It is natural to read it to claim that we do not check the
> .gitattributes files that are checked out in the working trees,
> which is utterly incorrect.
>
> >> it either
> >> checks the index or the files directly.
>
> > This means we cannot check the
> > attributes for a file against a certain revision.
>
> Whenever one is tempted to say "This means", one should realize that
> one does not have absolute confidence in whatever written before it,
> in other words, without additional explanation, one suspects that
> what one wanted to say would not be understood.
>
> A good piece of advice for such a person is to try rewriting WITHOUT
> anything before (and including) "This means".  And I think this is a
> good example to which the advice applies well.
>

I agree with what you're saying here. I think that's excellent advice,
too. Thanks!

>     There is no way with "git check-attr" to apply attributes from
>     .gitattributes files recorded in the same treeish to paths in a
>     treeish object.
>
> Our usual preference is to (1) start by describing the current state
> and (2) propose what can be done by deviating from it, in that
> order, so one might write it like so:
>
>     The contents of the .gitattributes files may evolve over time,
>     but "git check-attr" always checks attributes against them in
>     the working tree and/or in the index.  It may be beneficial to
>     optionally allow the version of .gitattributes found in the same
>     commit when checking the attributes for paths in an older commit.
>

Furthermore, I think you've put it nice here, I will copy this over and modify
the last statement to:

    It may be beneficial to optionally allow the users to check attributes
    against paths from older commits.

> By the way, applying the attributes from the working tree is by
> design and it should stay to be the default.  People are almost
> always working near the tip of the history, and working tree files
> are by definition ahead of any committed version---it is a feature
> that users can correct attribute definitions in their working tree
> files and then apply them to paths in the committed version.
>

Yeah, this was my understanding as well, I don't think I tried to change this or
implied the same anywhere.

> >> Add a new flag `--revision`/`-r` which will allow it work with
> >> revisions. This command will now, instead of checking the files/index,
> >> try and receive the blob for the given attribute file against the
> >> provided revision. The flag overrides checking against the index and
> >> filesystem and also works with bare repositories.
> >
> > The system, global and the attributes in .git/info/attributes from the
> > filesystem are still used. It would be useful to document that and
> > explain in the commit message why that is useful when using -r.
> >
> > -r is documented as accepting a revision but actually accepts any
> >  tree. That means a user can pass "-r HEAD:subdirectory" and all the
> >  attributes will be looked up as if subdirectory was the root
> >  directory of the repository which might be confusing. It would be
> >  helpful to know if passing a tree rather than a revision is
> >  useful. If it isn't then you could use lookup_commit_reference() to
> > ensure the user passes a revision.
>
> Unless you use ancestry relationships in any way [*], you do not
> want to require commits when an operation only requires trees.  In
> this case, taking tree-ish and documenting it as such is the right
> thing to do.
>
> [Footnote]
>
> * A good example that makes sense to limit to commit-ishes is when
>   merging two histories (without requiring the user to supply the
>   merge-base). You'd need to compute the merge-bases, so you require
>   two committishes and it is not enough to take two trees.

Will leave it as it is then.

Thanks both for the review. I think I will push a version 3 now,
mostly changes would be:
1. Documentation
2. Commit message

Also, it has been a while for me on this list, but I did notice this
topic missing from the
`What's cooking in git.git` mail, do I need to do something further?

--
- Karthik
diff mbox series

Patch

diff --git a/Documentation/git-check-attr.txt b/Documentation/git-check-attr.txt
index 84f41a8e82..3dc61f0fdc 100644
--- a/Documentation/git-check-attr.txt
+++ b/Documentation/git-check-attr.txt
@@ -9,8 +9,8 @@  git-check-attr - Display gitattributes information
 SYNOPSIS
 --------
 [verse]
-'git check-attr' [-a | --all | <attr>...] [--] <pathname>...
-'git check-attr' --stdin [-z] [-a | --all | <attr>...]
+'git check-attr' [-a | --all | <attr>...] [-r <revision>] [--] <pathname>...
+'git check-attr' --stdin [-z] [-a | --all | <attr>...] [-r <revision>]
 
 DESCRIPTION
 -----------
@@ -36,6 +36,10 @@  OPTIONS
 	If `--stdin` is also given, input paths are separated
 	with a NUL character instead of a linefeed character.
 
+--r <revision>::
+--revision=<revision>::
+	Check attributes against the specified revision.
+
 \--::
 	Interpret all preceding arguments as attributes and all following
 	arguments as path names.
diff --git a/archive.c b/archive.c
index 941495f5d7..81ff76fce9 100644
--- a/archive.c
+++ b/archive.c
@@ -120,7 +120,7 @@  static const struct attr_check *get_archive_attrs(struct index_state *istate,
 	static struct attr_check *check;
 	if (!check)
 		check = attr_check_initl("export-ignore", "export-subst", NULL);
-	git_check_attr(istate, path, check);
+	git_check_attr(istate, NULL, path, check);
 	return check;
 }
 
diff --git a/attr.c b/attr.c
index 42ad6de8c7..99883024ec 100644
--- a/attr.c
+++ b/attr.c
@@ -11,8 +11,13 @@ 
 #include "exec-cmd.h"
 #include "attr.h"
 #include "dir.h"
+#include "git-compat-util.h"
+#include "strbuf.h"
+#include "tree-walk.h"
 #include "utf8.h"
 #include "quote.h"
+#include "revision.h"
+#include "object-store.h"
 #include "thread-utils.h"
 
 const char git_attr__true[] = "(builtin)true";
@@ -729,14 +734,62 @@  static struct attr_stack *read_attr_from_file(const char *path, unsigned flags)
 	return res;
 }
 
-static struct attr_stack *read_attr_from_index(struct index_state *istate,
-					       const char *path,
-					       unsigned flags)
+static struct attr_stack *read_attr_from_buf(char *buf, const char *path,
+					     unsigned flags)
 {
 	struct attr_stack *res;
-	char *buf, *sp;
+	char *sp;
 	int lineno = 0;
 
+	if (!buf)
+		return NULL;
+
+	CALLOC_ARRAY(res, 1);
+	for (sp = buf; *sp;) {
+		char *ep;
+		int more;
+
+		ep = strchrnul(sp, '\n');
+		more = (*ep == '\n');
+		*ep = '\0';
+		handle_attr_line(res, sp, path, ++lineno, flags);
+		sp = ep + more;
+	}
+	free(buf);
+
+	return res;
+}
+
+static struct attr_stack *read_attr_from_blob(struct index_state *istate,
+					      const struct object_id *tree_oid,
+					      const char *path, unsigned flags)
+{
+	struct object_id oid;
+	unsigned long sz;
+	enum object_type type;
+	void *buf;
+	unsigned short mode;
+
+	if (!tree_oid)
+		return NULL;
+
+	if (get_tree_entry(istate->repo, tree_oid, path, &oid, &mode))
+		return NULL;
+
+	buf = read_object_file(&oid, &type, &sz);
+	if (!buf || type != OBJ_BLOB) {
+		free(buf);
+		return NULL;
+	}
+
+	return read_attr_from_buf(buf, path, flags);
+}
+
+static struct attr_stack *read_attr_from_index(struct index_state *istate,
+					       const char *path, unsigned flags)
+{
+	char *buf;
+
 	if (!istate)
 		return NULL;
 
@@ -758,28 +811,19 @@  static struct attr_stack *read_attr_from_index(struct index_state *istate,
 	if (!buf)
 		return NULL;
 
-	CALLOC_ARRAY(res, 1);
-	for (sp = buf; *sp; ) {
-		char *ep;
-		int more;
-
-		ep = strchrnul(sp, '\n');
-		more = (*ep == '\n');
-		*ep = '\0';
-		handle_attr_line(res, sp, path, ++lineno, flags);
-		sp = ep + more;
-	}
-	free(buf);
-	return res;
+	return read_attr_from_buf(buf, path, flags);
 }
 
 static struct attr_stack *read_attr(struct index_state *istate,
+				    const struct object_id *tree_oid,
 				    const char *path, unsigned flags)
 {
 	struct attr_stack *res = NULL;
 
 	if (direction == GIT_ATTR_INDEX) {
 		res = read_attr_from_index(istate, path, flags);
+	} else if (tree_oid) {
+		res = read_attr_from_blob(istate, tree_oid, path, flags);
 	} else if (!is_bare_repository()) {
 		if (direction == GIT_ATTR_CHECKOUT) {
 			res = read_attr_from_index(istate, path, flags);
@@ -839,6 +883,7 @@  static void push_stack(struct attr_stack **attr_stack_p,
 }
 
 static void bootstrap_attr_stack(struct index_state *istate,
+				 const struct object_id *tree_oid,
 				 struct attr_stack **stack)
 {
 	struct attr_stack *e;
@@ -864,7 +909,7 @@  static void bootstrap_attr_stack(struct index_state *istate,
 	}
 
 	/* root directory */
-	e = read_attr(istate, GITATTRIBUTES_FILE, flags | READ_ATTR_NOFOLLOW);
+	e = read_attr(istate, tree_oid, GITATTRIBUTES_FILE, flags | READ_ATTR_NOFOLLOW);
 	push_stack(stack, e, xstrdup(""), 0);
 
 	/* info frame */
@@ -878,6 +923,7 @@  static void bootstrap_attr_stack(struct index_state *istate,
 }
 
 static void prepare_attr_stack(struct index_state *istate,
+			       const struct object_id *tree_oid,
 			       const char *path, int dirlen,
 			       struct attr_stack **stack)
 {
@@ -899,7 +945,7 @@  static void prepare_attr_stack(struct index_state *istate,
 	 * .gitattributes in deeper directories to shallower ones,
 	 * and finally use the built-in set as the default.
 	 */
-	bootstrap_attr_stack(istate, stack);
+	bootstrap_attr_stack(istate, tree_oid, stack);
 
 	/*
 	 * Pop the "info" one that is always at the top of the stack.
@@ -954,7 +1000,7 @@  static void prepare_attr_stack(struct index_state *istate,
 		strbuf_add(&pathbuf, path + pathbuf.len, (len - pathbuf.len));
 		strbuf_addf(&pathbuf, "/%s", GITATTRIBUTES_FILE);
 
-		next = read_attr(istate, pathbuf.buf, READ_ATTR_NOFOLLOW);
+		next = read_attr(istate, tree_oid, pathbuf.buf, READ_ATTR_NOFOLLOW);
 
 		/* reset the pathbuf to not include "/.gitattributes" */
 		strbuf_setlen(&pathbuf, len);
@@ -1074,8 +1120,8 @@  static void determine_macros(struct all_attrs_item *all_attrs,
  * Otherwise all attributes are collected.
  */
 static void collect_some_attrs(struct index_state *istate,
-			       const char *path,
-			       struct attr_check *check)
+			       const struct object_id *tree_oid,
+			       const char *path, struct attr_check *check)
 {
 	int pathlen, rem, dirlen;
 	const char *cp, *last_slash = NULL;
@@ -1094,7 +1140,7 @@  static void collect_some_attrs(struct index_state *istate,
 		dirlen = 0;
 	}
 
-	prepare_attr_stack(istate, path, dirlen, &check->stack);
+	prepare_attr_stack(istate, tree_oid, path, dirlen, &check->stack);
 	all_attrs_init(&g_attr_hashmap, check);
 	determine_macros(check->all_attrs, check->stack);
 
@@ -1103,12 +1149,12 @@  static void collect_some_attrs(struct index_state *istate,
 }
 
 void git_check_attr(struct index_state *istate,
-		    const char *path,
+		    const struct object_id *tree_oid, const char *path,
 		    struct attr_check *check)
 {
 	int i;
 
-	collect_some_attrs(istate, path, check);
+	collect_some_attrs(istate, tree_oid, path, check);
 
 	for (i = 0; i < check->nr; i++) {
 		size_t n = check->items[i].attr->attr_nr;
@@ -1119,13 +1165,13 @@  void git_check_attr(struct index_state *istate,
 	}
 }
 
-void git_all_attrs(struct index_state *istate,
+void git_all_attrs(struct index_state *istate, const struct object_id *tree_oid,
 		   const char *path, struct attr_check *check)
 {
 	int i;
 
 	attr_check_reset(check);
-	collect_some_attrs(istate, path, check);
+	collect_some_attrs(istate, tree_oid, path, check);
 
 	for (i = 0; i < check->all_attrs_nr; i++) {
 		const char *name = check->all_attrs[i].attr->name;
diff --git a/attr.h b/attr.h
index 3fb40cced0..f4a2bedd68 100644
--- a/attr.h
+++ b/attr.h
@@ -1,6 +1,8 @@ 
 #ifndef ATTR_H
 #define ATTR_H
 
+#include "hash.h"
+
 /**
  * gitattributes mechanism gives a uniform way to associate various attributes
  * to set of paths.
@@ -190,13 +192,14 @@  void attr_check_free(struct attr_check *check);
 const char *git_attr_name(const struct git_attr *);
 
 void git_check_attr(struct index_state *istate,
-		    const char *path, struct attr_check *check);
+		    const struct object_id *tree_oid, const char *path,
+		    struct attr_check *check);
 
 /*
  * Retrieve all attributes that apply to the specified path.
  * check holds the attributes and their values.
  */
-void git_all_attrs(struct index_state *istate,
+void git_all_attrs(struct index_state *istate, const struct object_id *tree_oid,
 		   const char *path, struct attr_check *check);
 
 enum git_attr_direction {
diff --git a/builtin/check-attr.c b/builtin/check-attr.c
index 0fef10eb6b..28da31c2a5 100644
--- a/builtin/check-attr.c
+++ b/builtin/check-attr.c
@@ -1,3 +1,4 @@ 
+#include "repository.h"
 #define USE_THE_INDEX_VARIABLE
 #include "builtin.h"
 #include "cache.h"
@@ -9,9 +10,10 @@ 
 static int all_attrs;
 static int cached_attrs;
 static int stdin_paths;
+static char *revision;
 static const char * const check_attr_usage[] = {
-N_("git check-attr [-a | --all | <attr>...] [--] <pathname>..."),
-N_("git check-attr --stdin [-z] [-a | --all | <attr>...]"),
+N_("git check-attr [-a | --all | <attr>...] [-r <revision>] [--] <pathname>..."),
+N_("git check-attr --stdin [-z] [-a | --all | <attr>...] [-r <revision>]"),
 NULL
 };
 
@@ -23,6 +25,7 @@  static const struct option check_attr_options[] = {
 	OPT_BOOL(0 , "stdin", &stdin_paths, N_("read file names from stdin")),
 	OPT_BOOL('z', NULL, &nul_term_line,
 		 N_("terminate input and output records by a NUL character")),
+	OPT_STRING('r', "revision", &revision, N_("revision"), N_("check attributes at this revision")),
 	OPT_END()
 };
 
@@ -55,27 +58,26 @@  static void output_attr(struct attr_check *check, const char *file)
 	}
 }
 
-static void check_attr(const char *prefix,
-		       struct attr_check *check,
-		       int collect_all,
+static void check_attr(const char *prefix, struct attr_check *check,
+		       const struct object_id *tree_oid, int collect_all,
 		       const char *file)
+
 {
 	char *full_path =
 		prefix_path(prefix, prefix ? strlen(prefix) : 0, file);
 
 	if (collect_all) {
-		git_all_attrs(&the_index, full_path, check);
+		git_all_attrs(&the_index, tree_oid, full_path, check);
 	} else {
-		git_check_attr(&the_index, full_path, check);
+		git_check_attr(&the_index, tree_oid, full_path, check);
 	}
 	output_attr(check, file);
 
 	free(full_path);
 }
 
-static void check_attr_stdin_paths(const char *prefix,
-				   struct attr_check *check,
-				   int collect_all)
+static void check_attr_stdin_paths(const char *prefix, struct attr_check *check,
+				   const struct object_id *tree_oid, int collect_all)
 {
 	struct strbuf buf = STRBUF_INIT;
 	struct strbuf unquoted = STRBUF_INIT;
@@ -89,7 +91,7 @@  static void check_attr_stdin_paths(const char *prefix,
 				die("line is badly quoted");
 			strbuf_swap(&buf, &unquoted);
 		}
-		check_attr(prefix, check, collect_all, buf.buf);
+		check_attr(prefix, check, tree_oid, collect_all, buf.buf);
 		maybe_flush_or_die(stdout, "attribute to stdout");
 	}
 	strbuf_release(&buf);
@@ -105,6 +107,7 @@  static NORETURN void error_with_usage(const char *msg)
 int cmd_check_attr(int argc, const char **argv, const char *prefix)
 {
 	struct attr_check *check;
+	struct object_id tree_oid;
 	int cnt, i, doubledash, filei;
 
 	if (!is_bare_repository())
@@ -176,11 +179,15 @@  int cmd_check_attr(int argc, const char **argv, const char *prefix)
 		}
 	}
 
+	if (revision)
+		if (repo_get_oid_tree(the_repository, revision, &tree_oid))
+			error("%s: not a valid revision", revision);
+
 	if (stdin_paths)
-		check_attr_stdin_paths(prefix, check, all_attrs);
+		check_attr_stdin_paths(prefix, check, &tree_oid, all_attrs);
 	else {
 		for (i = filei; i < argc; i++)
-			check_attr(prefix, check, all_attrs, argv[i]);
+			check_attr(prefix, check, &tree_oid, all_attrs, argv[i]);
 		maybe_flush_or_die(stdout, "attribute to stdout");
 	}
 
diff --git a/builtin/pack-objects.c b/builtin/pack-objects.c
index 573d0b20b7..89535cfa6a 100644
--- a/builtin/pack-objects.c
+++ b/builtin/pack-objects.c
@@ -1318,7 +1318,7 @@  static int no_try_delta(const char *path)
 
 	if (!check)
 		check = attr_check_initl("delta", NULL);
-	git_check_attr(the_repository->index, path, check);
+	git_check_attr(the_repository->index, NULL, path, check);
 	if (ATTR_FALSE(check->items[0].value))
 		return 1;
 	return 0;
diff --git a/convert.c b/convert.c
index 9b67649032..a54d1690c0 100644
--- a/convert.c
+++ b/convert.c
@@ -1308,7 +1308,7 @@  void convert_attrs(struct index_state *istate,
 		git_config(read_convert_config, NULL);
 	}
 
-	git_check_attr(istate, path, check);
+	git_check_attr(istate, NULL, path, check);
 	ccheck = check->items;
 	ca->crlf_action = git_path_check_crlf(ccheck + 4);
 	if (ca->crlf_action == CRLF_UNDEFINED)
diff --git a/ll-merge.c b/ll-merge.c
index 22a603e8af..130d26501c 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -391,7 +391,7 @@  enum ll_merge_result ll_merge(mmbuffer_t *result_buf,
 		normalize_file(theirs, path, istate);
 	}
 
-	git_check_attr(istate, path, check);
+	git_check_attr(istate, NULL, path, check);
 	ll_driver_name = check->items[0].value;
 	if (check->items[1].value) {
 		marker_size = atoi(check->items[1].value);
@@ -419,7 +419,7 @@  int ll_merge_marker_size(struct index_state *istate, const char *path)
 
 	if (!check)
 		check = attr_check_initl("conflict-marker-size", NULL);
-	git_check_attr(istate, path, check);
+	git_check_attr(istate, NULL, path, check);
 	if (check->items[0].value) {
 		marker_size = atoi(check->items[0].value);
 		if (marker_size <= 0)
diff --git a/pathspec.c b/pathspec.c
index 46e77a85fe..48dec2c709 100644
--- a/pathspec.c
+++ b/pathspec.c
@@ -732,7 +732,7 @@  int match_pathspec_attrs(struct index_state *istate,
 	if (name[namelen])
 		name = to_free = xmemdupz(name, namelen);
 
-	git_check_attr(istate, name, item->attr_check);
+	git_check_attr(istate, NULL, name, item->attr_check);
 
 	free(to_free);
 
diff --git a/t/t0003-attributes.sh b/t/t0003-attributes.sh
index b3aabb8aa3..042af0239f 100755
--- a/t/t0003-attributes.sh
+++ b/t/t0003-attributes.sh
@@ -25,7 +25,14 @@  attr_check_quote () {
 	git check-attr test -- "$path" >actual &&
 	echo "\"$quoted_path\": test: $expect" >expect &&
 	test_cmp expect actual
+}
+
+attr_check_revision () {
+	path="$1" expect="$2" revision="$3" git_opts="$4" &&
 
+	git $git_opts check-attr -r $revision test -- "$path" >actual 2>err &&
+	echo "$path: test: $expect" >expect &&
+	test_cmp expect actual
 }
 
 test_expect_success 'open-quoted pathname' '
@@ -33,7 +40,6 @@  test_expect_success 'open-quoted pathname' '
 	attr_check a unspecified
 '
 
-
 test_expect_success 'setup' '
 	mkdir -p a/b/d a/c b &&
 	(
@@ -80,12 +86,38 @@  test_expect_success 'setup' '
 	EOF
 '
 
+test_expect_success 'setup branches' '
+	(
+		echo "f	test=f" &&
+		echo "a/i test=n"
+	) | git hash-object -w --stdin >id &&
+	git update-index --add --cacheinfo 100644,$(cat id),foo/bar/.gitattributes &&
+	git write-tree >id &&
+	tree_id=$(cat id) &&
+	git commit-tree $tree_id -m "random commit message" >id &&
+	commit_id=$(cat id) &&
+	git update-ref refs/heads/branch1 $commit_id &&
+
+	(
+		echo "g test=g" &&
+		echo "a/i test=m"
+	) | git hash-object -w --stdin >id &&
+	git update-index --add --cacheinfo 100644,$(cat id),foo/bar/.gitattributes &&
+	git write-tree >id &&
+	tree_id=$(cat id) &&
+	git commit-tree $tree_id -m "random commit message" >id &&
+	commit_id=$(cat id) &&
+	git update-ref refs/heads/branch2 $commit_id
+'
+
 test_expect_success 'command line checks' '
 	test_must_fail git check-attr &&
 	test_must_fail git check-attr -- &&
 	test_must_fail git check-attr test &&
 	test_must_fail git check-attr test -- &&
 	test_must_fail git check-attr -- f &&
+	test_must_fail git check-attr -r &&
+	test_must_fail git check-attr -r not-a-valid-ref &&
 	echo "f" | test_must_fail git check-attr --stdin &&
 	echo "f" | test_must_fail git check-attr --stdin -- f &&
 	echo "f" | test_must_fail git check-attr --stdin test -- f &&
@@ -287,6 +319,15 @@  test_expect_success 'using --git-dir and --work-tree' '
 	)
 '
 
+test_expect_success 'using --revision' '
+	attr_check_revision foo/bar/f f branch1 &&
+	attr_check_revision foo/bar/a/i n branch1 &&
+	attr_check_revision foo/bar/f unspecified branch2 &&
+	attr_check_revision foo/bar/a/i m branch2 &&
+	attr_check_revision foo/bar/g g branch2 &&
+	attr_check_revision foo/bar/g unspecified branch1
+'
+
 test_expect_success 'setup bare' '
 	git clone --template= --bare . bare.git
 '
@@ -306,6 +347,27 @@  test_expect_success 'bare repository: check that .gitattribute is ignored' '
 	)
 '
 
+test_expect_success 'bare repository: with --revision' '
+	(
+		cd bare.git &&
+		(
+			echo "f	test=f" &&
+			echo "a/i test=a/i"
+		) | git hash-object -w --stdin >id &&
+		git update-index --add --cacheinfo 100644 $(cat id) .gitattributes &&
+		git write-tree >id &&
+		tree_id=$(cat id) &&
+		git commit-tree $tree_id -m "random commit message" >id &&
+		commit_id=$(cat id) &&
+		git update-ref refs/heads/master $commit_id &&
+		attr_check_revision f f HEAD &&
+		attr_check_revision a/f f HEAD &&
+		attr_check_revision a/c/f f HEAD &&
+		attr_check_revision a/i a/i HEAD &&
+		attr_check_revision subdir/a/i unspecified HEAD
+	)
+'
+
 test_expect_success 'bare repository: check that --cached honors index' '
 	(
 		cd bare.git &&
diff --git a/userdiff.c b/userdiff.c
index 151d9a5278..b66f090a0b 100644
--- a/userdiff.c
+++ b/userdiff.c
@@ -412,7 +412,7 @@  struct userdiff_driver *userdiff_find_by_path(struct index_state *istate,
 		check = attr_check_initl("diff", NULL);
 	if (!path)
 		return NULL;
-	git_check_attr(istate, path, check);
+	git_check_attr(istate, NULL, path, check);
 
 	if (ATTR_TRUE(check->items[0].value))
 		return &driver_true;
diff --git a/ws.c b/ws.c
index 6e69877f25..eadbbe5667 100644
--- a/ws.c
+++ b/ws.c
@@ -78,7 +78,7 @@  unsigned whitespace_rule(struct index_state *istate, const char *pathname)
 	if (!attr_whitespace_rule)
 		attr_whitespace_rule = attr_check_initl("whitespace", NULL);
 
-	git_check_attr(istate, pathname, attr_whitespace_rule);
+	git_check_attr(istate, NULL, pathname, attr_whitespace_rule);
 	value = attr_whitespace_rule->items[0].value;
 	if (ATTR_TRUE(value)) {
 		/* true (whitespace) */