[v2,0/6] scalar: implement the subcommand "diagnose"

Message ID	pull.1128.v2.git.1644187146.gitgitgadget@gmail.com (mailing list archive)
Headers	show Return-Path: <git-owner@kernel.org> Message-Id: <pull.1128.v2.git.1644187146.gitgitgadget@gmail.com> In-Reply-To: <pull.1128.git.1643186507.gitgitgadget@gmail.com> References: <pull.1128.git.1643186507.gitgitgadget@gmail.com> From: "Johannes Schindelin via GitGitGadget" <gitgitgadget@gmail.com> Date: Sun, 06 Feb 2022 22:39:00 +0000 Subject: [PATCH v2 0/6] scalar: implement the subcommand "diagnose" Fcc: Sent Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit MIME-Version: 1.0 To: git@vger.kernel.org Cc: =?utf-8?b?UmVuw6k=?= Scharfe <l.s.r@web.de>, Taylor Blau <me@ttaylorr.com>, Derrick Stolee <stolee@gmail.com>, Elijah Newren <newren@gmail.com>, Johannes Schindelin <johannes.schindelin@gmx.de> Precedence: bulk
Series	scalar: implement the subcommand "diagnose" \| expand [v2,0/6] scalar: implement the subcommand "diagnose" [v2,1/6] archive: optionally add "virtual" files [v2,2/6] scalar: validate the optional enlistment argument [v2,3/6] Implement `scalar diagnose` [v2,4/6] scalar diagnose: include disk space information [v2,5/6] scalar: teach `diagnose` to gather packfile info [v2,6/6] scalar: teach `diagnose` to gather loose objects information

Over the course of the years, we developed a sub-command that gathers diagnostic data into a .zip file that can then be attached to bug reports. This sub-command turned out to be very useful in helping Scalar developers identify and fix issues. Changes since v1: * Instead of creating a throw-away repository, staging the contents of the .zip file and then using git write-tree and git archive to write the .zip file, the patch series now introduces a new option to git archive and uses write_archive() directly (avoiding any separate process). * Since the command avoids separate processes, it is now blazing fast on Windows, and I dropped the spinner() function because it's no longer needed. * While reworking the test case, I noticed that scalar [...] <enlistment> failed to verify that the specified directory exists, and would happily "traverse to its parent directory" on its quest to find a Scalar enlistment. That is of course incorrect, and has been fixed as a "while at it" sort of preparatory commit. * I had forgotten to sign off on all the commits, which has been fixed. * Instead of some "home-grown" readdir()-based function, the code now uses for_each_file_in_pack_dir() to look through the pack directories. * If any alternates are configured, their pack directories are now included in the output. * The commit message that might be interpreted to promise information about large loose files has been corrected to no longer promise that. * The test cases have been adjusted to test a little bit more (e.g. verifying that specific paths are mentioned in the output, instead of merely verifying that the output is non-empty). Johannes Schindelin (4): archive: optionally add "virtual" files scalar: validate the optional enlistment argument Implement `scalar diagnose` scalar diagnose: include disk space information Matthew John Cheetham (2): scalar: teach `diagnose` to gather packfile info scalar: teach `diagnose` to gather loose objects information Documentation/git-archive.txt | 11 ++ archive.c | 51 +++++- contrib/scalar/scalar.c | 291 ++++++++++++++++++++++++++++++- contrib/scalar/scalar.txt | 12 ++ contrib/scalar/t/t9099-scalar.sh | 27 +++ t/t5003-archive-zip.sh | 12 ++ 6 files changed, 394 insertions(+), 10 deletions(-) base-commit: ddc35d833dd6f9e8946b09cecd3311b8aa18d295 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1128%2Fdscho%2Fscalar-diagnose-v2 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1128/dscho/scalar-diagnose-v2 Pull-Request: https://github.com/gitgitgadget/git/pull/1128 Range-diff vs v1: -: ----------- > 1: 49ff3c1f2b3 archive: optionally add "virtual" files -: ----------- > 2: 600da8d465e scalar: validate the optional enlistment argument 1: ce85506e7a4 ! 3: 0d570137bb6 Implement `scalar diagnose` @@ Commit message Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> ## contrib/scalar/scalar.c ## +@@ + #include "dir.h" + #include "packfile.h" + #include "help.h" ++#include "archive.h" + + /* + * Remove the deepest subdirectory in the provided path string. Path must not @@ contrib/scalar/scalar.c: static int unregister_dir(void) return res; } -+static int stage(const char *git_dir, struct strbuf *buf, const char *path) -+{ -+ struct strbuf cacheinfo = STRBUF_INIT; -+ struct child_process cp = CHILD_PROCESS_INIT; -+ int res; -+ -+ strbuf_addstr(&cacheinfo, "100644,"); -+ -+ cp.git_cmd = 1; -+ strvec_pushl(&cp.args, "--git-dir", git_dir, -+ "hash-object", "-w", "--stdin", NULL); -+ res = pipe_command(&cp, buf->buf, buf->len, &cacheinfo, 256, NULL, 0); -+ if (!res) { -+ strbuf_rtrim(&cacheinfo); -+ strbuf_addch(&cacheinfo, ','); -+ /* We cannot stage `.git`, use `_git` instead. */ -+ if (starts_with(path, ".git/")) -+ strbuf_addf(&cacheinfo, "_%s", path + 1); -+ else -+ strbuf_addstr(&cacheinfo, path); -+ -+ child_process_init(&cp); -+ cp.git_cmd = 1; -+ strvec_pushl(&cp.args, "--git-dir", git_dir, -+ "update-index", "--add", "--cacheinfo", -+ cacheinfo.buf, NULL); -+ res = run_command(&cp); -+ } -+ -+ strbuf_release(&cacheinfo); -+ return res; -+} -+ -+static int stage_file(const char *git_dir, const char *path) -+{ -+ struct strbuf buf = STRBUF_INIT; -+ int res; -+ -+ if (strbuf_read_file(&buf, path, 0) < 0) -+ return error(_("could not read '%s'"), path); -+ -+ res = stage(git_dir, &buf, path); -+ -+ strbuf_release(&buf); -+ return res; -+} -+ -+static int stage_directory(const char *git_dir, const char *path, int recurse) ++static int add_directory_to_archiver(struct strvec *archiver_args, ++ const char *path, int recurse) +{ + int at_root = !*path; + DIR *dir = opendir(at_root ? "." : path); @@ contrib/scalar/scalar.c: static int unregister_dir(void) + if (!at_root) + strbuf_addf(&buf, "%s/", path); + len = buf.len; ++ strvec_pushf(archiver_args, "--prefix=%s", buf.buf); + + while (!res && (e = readdir(dir))) { + if (!strcmp(".", e->d_name) || !strcmp("..", e->d_name)) @@ contrib/scalar/scalar.c: static int unregister_dir(void) + strbuf_setlen(&buf, len); + strbuf_addstr(&buf, e->d_name); + -+ if ((e->d_type == DT_REG && stage_file(git_dir, buf.buf)) || -+ (e->d_type == DT_DIR && recurse && -+ stage_directory(git_dir, buf.buf, recurse))) ++ if (e->d_type == DT_REG) ++ strvec_pushf(archiver_args, "--add-file=%s", buf.buf); ++ else if (e->d_type != DT_DIR) + res = -1; ++ else if (recurse) ++ add_directory_to_archiver(archiver_args, buf.buf, recurse); + } + + closedir(dir); + strbuf_release(&buf); + return res; +} -+ -+static int index_to_zip(const char *git_dir) -+{ -+ struct child_process cp = CHILD_PROCESS_INIT; -+ struct strbuf oid = STRBUF_INIT; -+ -+ cp.git_cmd = 1; -+ strvec_pushl(&cp.args, "--git-dir", git_dir, "write-tree", NULL); -+ if (pipe_command(&cp, NULL, 0, &oid, the_hash_algo->hexsz + 1, -+ NULL, 0)) -+ return error(_("could not write temporary tree object")); -+ -+ strbuf_rtrim(&oid); -+ child_process_init(&cp); -+ cp.git_cmd = 1; -+ strvec_pushl(&cp.args, "--git-dir", git_dir, "archive", "-o", NULL); -+ strvec_pushf(&cp.args, "%s.zip", git_dir); -+ strvec_pushl(&cp.args, oid.buf, "--", NULL); -+ strbuf_release(&oid); -+ return run_command(&cp); -+} + /* printf-style interface, expects `<key>=<value>` argument */ static int set_config(const char *fmt, ...) @@ contrib/scalar/scalar.c: cleanup: + N_("scalar diagnose [<enlistment>]"), + NULL + }; -+ struct strbuf tmp_dir = STRBUF_INIT; ++ struct strbuf zip_path = STRBUF_INIT; ++ struct strvec archiver_args = STRVEC_INIT; ++ char **argv_copy = NULL; ++ int stdout_fd = -1, archiver_fd = -1; + time_t now = time(NULL); + struct tm tm; + struct strbuf path = STRBUF_INIT, buf = STRBUF_INIT; ++ size_t off; + int res = 0; + + argc = parse_options(argc, argv, NULL, options, + usage, 0); + -+ setup_enlistment_directory(argc, argv, usage, options, &buf); ++ setup_enlistment_directory(argc, argv, usage, options, &zip_path); ++ ++ strbuf_addstr(&zip_path, "/.scalarDiagnostics/scalar_"); ++ strbuf_addftime(&zip_path, ++ "%Y%m%d_%H%M%S", localtime_r(&now, &tm), 0, 0); ++ strbuf_addstr(&zip_path, ".zip"); ++ switch (safe_create_leading_directories(zip_path.buf)) { ++ case SCLD_EXISTS: ++ case SCLD_OK: ++ break; ++ default: ++ error_errno(_("could not create directory for '%s'"), ++ zip_path.buf); ++ goto diagnose_cleanup; ++ } ++ stdout_fd = dup(1); ++ if (stdout_fd < 0) { ++ res = error_errno(_("could not duplicate stdout")); ++ goto diagnose_cleanup; ++ } + -+ strbuf_addstr(&buf, "/.scalarDiagnostics/scalar_"); -+ strbuf_addftime(&buf, "%Y%m%d_%H%M%S", localtime_r(&now, &tm), 0, 0); -+ if (run_git("init", "-q", "-b", "dummy", "--bare", buf.buf, NULL)) { -+ res = error(_("could not initialize temporary repository: %s"), -+ buf.buf); ++ archiver_fd = xopen(zip_path.buf, O_CREAT | O_WRONLY | O_TRUNC, 0666); ++ if (archiver_fd < 0 || dup2(archiver_fd, 1) < 0) { ++ res = error_errno(_("could not redirect output")); + goto diagnose_cleanup; + } -+ strbuf_realpath(&tmp_dir, buf.buf, 1); + -+ strbuf_reset(&buf); -+ strbuf_addf(&buf, "Collecting diagnostic info into temp folder %s\n\n", -+ tmp_dir.buf); ++ init_zip_archiver(); ++ strvec_pushl(&archiver_args, "scalar-diagnose", "--format=zip", NULL); + ++ strbuf_reset(&buf); ++ strbuf_addstr(&buf, ++ "--add-file-with-content=diagnostics.log:" ++ "Collecting diagnostic info\n\n"); + get_version_info(&buf, 1); + + strbuf_addf(&buf, "Enlistment root: %s\n", the_repository->worktree); -+ fwrite(buf.buf, buf.len, 1, stdout); -+ -+ if ((res = stage(tmp_dir.buf, &buf, "diagnostics.log"))) -+ goto diagnose_cleanup; -+ -+ if ((res = stage_directory(tmp_dir.buf, ".git", 0)) || -+ (res = stage_directory(tmp_dir.buf, ".git/hooks", 0)) || -+ (res = stage_directory(tmp_dir.buf, ".git/info", 0)) || -+ (res = stage_directory(tmp_dir.buf, ".git/logs", 1)) || -+ (res = stage_directory(tmp_dir.buf, ".git/objects/info", 0))) ++ off = strchr(buf.buf, ':') + 1 - buf.buf; ++ write_or_die(stdout_fd, buf.buf + off, buf.len - off); ++ strvec_push(&archiver_args, buf.buf); ++ ++ if ((res = add_directory_to_archiver(&archiver_args, ".git", 0)) || ++ (res = add_directory_to_archiver(&archiver_args, ".git/hooks", 0)) || ++ (res = add_directory_to_archiver(&archiver_args, ".git/info", 0)) || ++ (res = add_directory_to_archiver(&archiver_args, ".git/logs", 1)) || ++ (res = add_directory_to_archiver(&archiver_args, ".git/objects/info", 0))) + goto diagnose_cleanup; + -+ res = index_to_zip(tmp_dir.buf); ++ strvec_pushl(&archiver_args, "--prefix=", ++ oid_to_hex(the_hash_algo->empty_tree), "--", NULL); + -+ if (!res) -+ res = remove_dir_recursively(&tmp_dir, 0); ++ /* `write_archive()` modifies the `argv` passed to it. Let it. */ ++ argv_copy = xmemdupz(archiver_args.v, ++ sizeof(char *) * archiver_args.nr); ++ res = write_archive(archiver_args.nr, (const char **)argv_copy, NULL, ++ the_repository, NULL, 0); ++ if (res) { ++ error(_("failed to write archive")); ++ goto diagnose_cleanup; ++ } + + if (!res) + printf("\n" + "Diagnostics complete.\n" -+ "All of the gathered info is captured in '%s.zip'\n", -+ tmp_dir.buf); ++ "All of the gathered info is captured in '%s'\n", ++ zip_path.buf); + +diagnose_cleanup: -+ strbuf_release(&tmp_dir); ++ if (archiver_fd >= 0) { ++ close(1); ++ dup2(stdout_fd, 1); ++ } ++ free(argv_copy); ++ strvec_clear(&archiver_args); ++ strbuf_release(&zip_path); + strbuf_release(&path); + strbuf_release(&buf); + @@ contrib/scalar/scalar.txt: reconfigure the enlistment. ## contrib/scalar/t/t9099-scalar.sh ## -@@ contrib/scalar/t/t9099-scalar.sh: test_expect_success 'scalar clone' ' - ) +@@ contrib/scalar/t/t9099-scalar.sh: test_expect_success '`scalar [...] <dir>` errors out when dir is missing' ' + grep "cloned. does not exist" err ' +SQ="'" +test_expect_success UNZIP 'scalar diagnose' ' ++ scalar clone "file://$(pwd)" cloned --single-branch && + scalar diagnose cloned >out && + sed -n "s/.*$SQ\$.*\\.zip\$$SQ.*/\\1/p" <out >zip_path && + zip_path=$(cat zip_path) && @@ contrib/scalar/t/t9099-scalar.sh: test_expect_success 'scalar clone' ' + test_file_not_empty out +' + - test_expect_success 'scalar reconfigure' ' - git init one/src && - scalar register one && + test_done 2: f8885b27502 ! 4: 938e38b5a09 scalar diagnose: include disk space information @@ Commit message Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> ## contrib/scalar/scalar.c ## -@@ contrib/scalar/scalar.c: static int index_to_zip(const char *git_dir) - return run_command(&cp); +@@ contrib/scalar/scalar.c: static int add_directory_to_archiver(struct strvec *archiver_args, + return res; } +#ifndef WIN32 @@ contrib/scalar/scalar.c: static int cmd_diagnose(int argc, const char **argv) strbuf_addf(&buf, "Enlistment root: %s\n", the_repository->worktree); + get_disk_info(&buf); - fwrite(buf.buf, buf.len, 1, stdout); - - if ((res = stage(tmp_dir.buf, &buf, "diagnostics.log"))) + off = strchr(buf.buf, ':') + 1 - buf.buf; + write_or_die(stdout_fd, buf.buf + off, buf.len - off); + strvec_push(&archiver_args, buf.buf); + + ## contrib/scalar/t/t9099-scalar.sh ## +@@ contrib/scalar/t/t9099-scalar.sh: SQ="'" + test_expect_success UNZIP 'scalar diagnose' ' + scalar clone "file://$(pwd)" cloned --single-branch && + scalar diagnose cloned >out && ++ grep "Available space" out && + sed -n "s/.*$SQ\$.*\\.zip\$$SQ.*/\\1/p" <out >zip_path && + zip_path=$(cat zip_path) && + test -n "$zip_path" && 3: 330b36de799 ! 5: bd9428919fa scalar: teach `diagnose` to gather packfile info @@ Metadata ## Commit message ## scalar: teach `diagnose` to gather packfile info - Teach the `scalar diagnose` command to gather file size information - about pack files. + It's helpful to see if there are other crud files in the pack + directory. Let's teach the `scalar diagnose` command to gather + file size information about pack files. + + While at it, also enumerate the pack files in the alternate + object directories, if any are registered. Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com> + Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> ## contrib/scalar/scalar.c ## +@@ + #include "packfile.h" + #include "help.h" + #include "archive.h" ++#include "object-store.h" + + /* + * Remove the deepest subdirectory in the provided path string. Path must not @@ contrib/scalar/scalar.c: cleanup: return res; } -+static void dir_file_stats(struct strbuf *buf, const char *path) ++static void dir_file_stats_objects(const char *full_path, size_t full_path_len, ++ const char *file_name, void *data) +{ -+ DIR *dir = opendir(path); -+ struct dirent *e; -+ struct stat e_stat; -+ struct strbuf file_path = STRBUF_INIT; -+ size_t base_path_len; ++ struct strbuf *buf = data; ++ struct stat st; + -+ if (!dir) -+ return; ++ if (!stat(full_path, &st)) ++ strbuf_addf(buf, "%-70s %16" PRIuMAX "\n", file_name, ++ (uintmax_t)st.st_size); ++} + -+ strbuf_addstr(buf, "Contents of "); -+ strbuf_add_absolute_path(buf, path); -+ strbuf_addstr(buf, ":\n"); ++static int dir_file_stats(struct object_directory *object_dir, void *data) ++{ ++ struct strbuf *buf = data; + -+ strbuf_add_absolute_path(&file_path, path); -+ strbuf_addch(&file_path, '/'); -+ base_path_len = file_path.len; ++ strbuf_addf(buf, "Contents of %s:\n", object_dir->path); + -+ while ((e = readdir(dir)) != NULL) -+ if (!is_dot_or_dotdot(e->d_name) && e->d_type == DT_REG) { -+ strbuf_setlen(&file_path, base_path_len); -+ strbuf_addstr(&file_path, e->d_name); -+ if (!stat(file_path.buf, &e_stat)) -+ strbuf_addf(buf, "%-70s %16"PRIuMAX"\n", -+ e->d_name, -+ (uintmax_t)e_stat.st_size); -+ } ++ for_each_file_in_pack_dir(object_dir->path, dir_file_stats_objects, ++ data); + -+ strbuf_release(&file_path); -+ closedir(dir); ++ return 0; +} + static int cmd_diagnose(int argc, const char **argv) { struct option options[] = { @@ contrib/scalar/scalar.c: static int cmd_diagnose(int argc, const char **argv) - if ((res = stage(tmp_dir.buf, &buf, "diagnostics.log"))) - goto diagnose_cleanup; + write_or_die(stdout_fd, buf.buf + off, buf.len - off); + strvec_push(&archiver_args, buf.buf); + strbuf_reset(&buf); -+ dir_file_stats(&buf, ".git/objects/pack"); -+ -+ if ((res = stage(tmp_dir.buf, &buf, "packs-local.txt"))) -+ goto diagnose_cleanup; ++ strbuf_addstr(&buf, "--add-file-with-content=packs-local.txt:"); ++ dir_file_stats(the_repository->objects->odb, &buf); ++ foreach_alt_odb(dir_file_stats, &buf); ++ strvec_push(&archiver_args, buf.buf); + - if ((res = stage_directory(tmp_dir.buf, ".git", 0)) || - (res = stage_directory(tmp_dir.buf, ".git/hooks", 0)) || - (res = stage_directory(tmp_dir.buf, ".git/info", 0)) || + if ((res = add_directory_to_archiver(&archiver_args, ".git", 0)) || + (res = add_directory_to_archiver(&archiver_args, ".git/hooks", 0)) || + (res = add_directory_to_archiver(&archiver_args, ".git/info", 0)) || ## contrib/scalar/t/t9099-scalar.sh ## +@@ contrib/scalar/t/t9099-scalar.sh: test_expect_success '`scalar [...] <dir>` errors out when dir is missing' ' + SQ="'" + test_expect_success UNZIP 'scalar diagnose' ' + scalar clone "file://$(pwd)" cloned --single-branch && ++ git repack && ++ echo "$(pwd)/.git/objects/" >>cloned/src/.git/objects/info/alternates && + scalar diagnose cloned >out && + grep "Available space" out && + sed -n "s/.*$SQ\$.*\\.zip\$$SQ.*/\\1/p" <out >zip_path && @@ contrib/scalar/t/t9099-scalar.sh: test_expect_success UNZIP 'scalar diagnose' ' folder=${zip_path%.zip} && test_path_is_missing "$folder" && unzip -p "$zip_path" diagnostics.log >out && +- test_file_not_empty out + test_file_not_empty out && + unzip -p "$zip_path" packs-local.txt >out && - test_file_not_empty out ++ grep "$(pwd)/.git/objects" out ' + test_done 4: 213f2c94b73 ! 6: 7a8875be425 scalar: teach `diagnose` to gather loose objects information @@ Commit message When operating at the scale that Scalar wants to support, certain data shapes are more likely to cause undesirable performance issues, such as - large numbers or large sizes of loose objects. + large numbers of loose objects. By including statistics about this, `scalar diagnose` now makes it easier to identify such scenarios. Signed-off-by: Matthew John Cheetham <mjcheetham@outlook.com> + Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de> ## contrib/scalar/scalar.c ## -@@ contrib/scalar/scalar.c: static void dir_file_stats(struct strbuf *buf, const char *path) - closedir(dir); +@@ contrib/scalar/scalar.c: static int dir_file_stats(struct object_directory *object_dir, void *data) + return 0; } +static int count_files(char *path) @@ contrib/scalar/scalar.c: static void dir_file_stats(struct strbuf *buf, const ch { struct option options[] = { @@ contrib/scalar/scalar.c: static int cmd_diagnose(int argc, const char **argv) - if ((res = stage(tmp_dir.buf, &buf, "packs-local.txt"))) - goto diagnose_cleanup; + foreach_alt_odb(dir_file_stats, &buf); + strvec_push(&archiver_args, buf.buf); + strbuf_reset(&buf); ++ strbuf_addstr(&buf, "--add-file-with-content=objects-local.txt:"); + loose_objs_stats(&buf, ".git/objects"); ++ strvec_push(&archiver_args, buf.buf); + -+ if ((res = stage(tmp_dir.buf, &buf, "objects-local.txt"))) -+ goto diagnose_cleanup; -+ - if ((res = stage_directory(tmp_dir.buf, ".git", 0)) || - (res = stage_directory(tmp_dir.buf, ".git/hooks", 0)) || - (res = stage_directory(tmp_dir.buf, ".git/info", 0)) || + if ((res = add_directory_to_archiver(&archiver_args, ".git", 0)) || + (res = add_directory_to_archiver(&archiver_args, ".git/hooks", 0)) || + (res = add_directory_to_archiver(&archiver_args, ".git/info", 0)) || ## contrib/scalar/t/t9099-scalar.sh ## +@@ contrib/scalar/t/t9099-scalar.sh: test_expect_success UNZIP 'scalar diagnose' ' + scalar clone "file://$(pwd)" cloned --single-branch && + git repack && + echo "$(pwd)/.git/objects/" >>cloned/src/.git/objects/info/alternates && ++ test_commit -C cloned/src loose && + scalar diagnose cloned >out && + grep "Available space" out && + sed -n "s/.*$SQ\$.*\\.zip\$$SQ.*/\\1/p" <out >zip_path && @@ contrib/scalar/t/t9099-scalar.sh: test_expect_success UNZIP 'scalar diagnose' ' unzip -p "$zip_path" diagnostics.log >out && test_file_not_empty out && unzip -p "$zip_path" packs-local.txt >out && -+ test_file_not_empty out && +- grep "$(pwd)/.git/objects" out ++ grep "$(pwd)/.git/objects" out && + unzip -p "$zip_path" objects-local.txt >out && - test_file_not_empty out ++ grep "^Total: [1-9]" out ' + test_done 5: 3a2cdce554a < -: ----------- scalar diagnose: show a spinner while staging content

[v2,0/6] scalar: implement the subcommand "diagnose"

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