[v2,5/8] shortlog: de-duplicate trailer values

Commit Message

Jeff King Sept. 27, 2020, 8:40 a.m. UTC

The current documentation is vague about what happens with
--group=trailer:signed-off-by when we see a commit with:

  Signed-off-by: One
  Signed-off-by: Two
  Signed-off-by: One

We clearly should credit both "One" and "Two", but should "One" get
credited twice? The current code does so, but mostly because that was
the easiest thing to do. It's probably more useful to count each commit
at most once. This will become especially important when we allow
values from multiple sources in a future patch.

Signed-off-by: Jeff King <[e-mail]>
---
 Documentation/git-shortlog.txt |  3 +-
 builtin/shortlog.c             | 58 ++++++++++++++++++++++++++++++++++
 t/t4201-shortlog.sh            | 28 ++++++++++++++++
 3 files changed, 88 insertions(+), 1 deletion(-)

Comments

Junio C Hamano Sept. 27, 2020, 8:23 p.m. UTC | #1

Jeff King <[e-mail]> writes:

> The current documentation is vague about what happens with
> --group=trailer:signed-off-by when we see a commit with:
>
>   Signed-off-by: One
>   Signed-off-by: Two
>   Signed-off-by: One
>
> We clearly should credit both "One" and "Two", but should "One" get
> credited twice? The current code does so, but mostly because that was
> the easiest thing to do.

I thought that "the current documentation" as of step 4/8 were quite
clear about double counting ;-).

> It's probably more useful to count each commit
> at most once. This will become especially important when we allow
> values from multiple sources in a future patch.

Yup.  Makes readers want to read further ;-)

Jeff King Sept. 28, 2020, 3:19 a.m. UTC | #2

On Sun, Sep 27, 2020 at 01:23:25PM -0700, Junio C Hamano wrote:

> Jeff King <[e-mail]> writes:
> 
> > The current documentation is vague about what happens with
> > --group=trailer:signed-off-by when we see a commit with:
> >
> >   Signed-off-by: One
> >   Signed-off-by: Two
> >   Signed-off-by: One
> >
> > We clearly should credit both "One" and "Two", but should "One" get
> > credited twice? The current code does so, but mostly because that was
> > the easiest thing to do.
> 
> I thought that "the current documentation" as of step 4/8 were quite
> clear about double counting ;-).

It was clear to me that the commit would be counted at least twice: once
for the "one" bucket and once for the "two" bucket, but not that it
would count twice for the "two" bucket. Or at least, I didn't think of
this issue at all back when I wrote the original patch long ago, and
only noticed the problem when I revisited it. :)

Anyway, I think the semantics at the end of the series are quite
sensible.

-Peff

Patch

diff --git a/Documentation/git-shortlog.txt b/Documentation/git-shortlog.txt
index edd6cda58a..9e94613e13 100644
--- a/Documentation/git-shortlog.txt
+++ b/Documentation/git-shortlog.txt
@@ -61,7 +61,8 @@  OPTIONS
 +
 Note that commits that do not include the trailer will not be counted.
 Likewise, commits with multiple trailers (e.g., multiple signoffs) may
-be counted more than once.
+be counted more than once (but only once per unique trailer value in
+that commit).
 +
 The contents of each trailer value are taken literally and completely.
 No mailmap is applied, and the `-e` option has no effect (if the trailer
diff --git a/builtin/shortlog.c b/builtin/shortlog.c
index e1d9ee909f..d2d8103dd3 100644
--- a/builtin/shortlog.c
+++ b/builtin/shortlog.c
@@ -166,13 +166,68 @@  static void read_from_stdin(struct shortlog *log)
 	strbuf_release(&oneline);
 }
 
+struct strset_item {
+	struct hashmap_entry ent;
+	char value[FLEX_ARRAY];
+};
+
+struct strset {
+	struct hashmap map;
+};
+
+#define STRSET_INIT { { NULL } }
+
+static int strset_item_hashcmp(const void *hash_data,
+			       const struct hashmap_entry *entry,
+			       const struct hashmap_entry *entry_or_key,
+			       const void *keydata)
+{
+	const struct strset_item *a, *b;
+
+	a = container_of(entry, const struct strset_item, ent);
+	if (keydata)
+		return strcmp(a->value, keydata);
+
+	b = container_of(entry_or_key, const struct strset_item, ent);
+	return strcmp(a->value, b->value);
+}
+
+/*
+ * Adds "str" to the set if it was not already present; returns true if it was
+ * already there.
+ */
+static int strset_check_and_add(struct strset *ss, const char *str)
+{
+	unsigned int hash = strhash(str);
+	struct strset_item *item;
+
+	if (!ss->map.table)
+		hashmap_init(&ss->map, strset_item_hashcmp, NULL, 0);
+
+	if (hashmap_get_from_hash(&ss->map, hash, str))
+		return 1;
+
+	FLEX_ALLOC_STR(item, value, str);
+	hashmap_entry_init(&item->ent, hash);
+	hashmap_add(&ss->map, &item->ent);
+	return 0;
+}
+
+static void strset_clear(struct strset *ss)
+{
+	if (!ss->map.table)
+		return;
+	hashmap_free_entries(&ss->map, struct strset_item, ent);
+}
+
 static void insert_records_from_trailers(struct shortlog *log,
 					 struct commit *commit,
 					 struct pretty_print_context *ctx,
 					 const char *oneline)
 {
 	struct trailer_iterator iter;
 	const char *commit_buffer, *body;
+	struct strset dups = STRSET_INIT;
 
 	/*
 	 * Using format_commit_message("%B") would be simpler here, but
@@ -190,10 +245,13 @@  static void insert_records_from_trailers(struct shortlog *log,
 		if (strcasecmp(iter.key.buf, log->trailer))
 			continue;
 
+		if (strset_check_and_add(&dups, value))
+			continue;
 		insert_one_record(log, value, oneline);
 	}
 	trailer_iterator_release(&iter);
 
+	strset_clear(&dups);
 	unuse_commit_buffer(commit, commit_buffer);
 }
 
diff --git a/t/t4201-shortlog.sh b/t/t4201-shortlog.sh
index e97d891a71..83dbbc44e8 100755
--- a/t/t4201-shortlog.sh
+++ b/t/t4201-shortlog.sh
@@ -234,4 +234,32 @@  test_expect_success 'shortlog --group=trailer:signed-off-by' '
 	test_cmp expect actual
 '
 
+test_expect_success 'shortlog de-duplicates trailers in a single commit' '
+	git commit --allow-empty -F - <<-\EOF &&
+	subject one
+
+	this message has two distinct values, plus a repeat
+
+	Repeated-trailer: Foo
+	Repeated-trailer: Bar
+	Repeated-trailer: Foo
+	EOF
+
+	git commit --allow-empty -F - <<-\EOF &&
+	subject two
+
+	similar to the previous, but without the second distinct value
+
+	Repeated-trailer: Foo
+	Repeated-trailer: Foo
+	EOF
+
+	cat >expect <<-\EOF &&
+	     2	Foo
+	     1	Bar
+	EOF
+	git shortlog -ns --group=trailer:repeated-trailer -2 HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_done