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[PATCH 1/3] builtin: introduce diff-blob command

From
Justin Tobler <jltobler@gmail.com>
Date
Dec 13, 2024, 04:23 UTC
Message-ID
<20241213042312.2890841-2-jltobler@gmail.com>
In-Reply-To
<20241213042312.2890841-1-jltobler@gmail.com>

Through git-diff(1), a single diff can be generated from a pair of blob revisions directly. This is useful when more explicit control over the set of diffs to compute is desired. Expanding on this, it would be useful to also support generating multiple diffs for blob pairs provided on stdin to faciliate batch processing in a single process. Batch blob diff processing is likely considered more of a plumbing feature so, instead of further extending the porcelain git-diff(1), a diff plumbing command should be used.

As there is not an existing diff plumbing command that handles blob diffs, introduce git-diff-blob(1) which generates a single diff between a specified pair of blobs following how the same operation is done in git-diff(1). While git-diff-blob(1) functionality is a direct subset of git-diff(1), a subsequent patch extends it to provide a new plumbing related feature.

The surrounding setup required for the new builtin is also added. An existing test for blob diffs through git-diff(1) is also modified to reuse its test cases for git-diff-blob(1).

Signed-off-by: Justin Tobler <jltobler@gmail.com>
---
 .gitignore                      |   1 +
 Documentation/git-diff-blob.txt |  29 ++++++++
 Documentation/meson.build       |   1 +
 Makefile                        |   1 +
 builtin.h                       |   1 +
 builtin/diff-blob.c             | 117 ++++++++++++++++++++++++++++++++
 command-list.txt                |   1 +
 git.c                           |   1 +
 meson.build                     |   1 +
 t/t4063-diff-blobs.sh           | 100 ++++++++++++++-------------
 10 files changed, 205 insertions(+), 48 deletions(-)
 create mode 100644 Documentation/git-diff-blob.txt
 create mode 100644 builtin/diff-blob.c
diff --git a/.gitignore b/.gitignore
index e82aa19df0..e7487072bd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -52,6 +52,7 @@
 /git-daemon
 /git-diagnose
 /git-diff
+/git-diff-blob
 /git-diff-files
 /git-diff-index
 /git-diff-tree
diff --git a/Documentation/git-diff-blob.txt b/Documentation/git-diff-blob.txt
new file mode 100644
index 0000000000..732992d1d7
--- /dev/null
+++ b/Documentation/git-diff-blob.txt
@@ -0,0 +1,29 @@
+git-diff-blob(1)
+================
+
+NAME
+----
+git-diff-blob - Compares the content and mode of two specified blobs
+
+
+SYNOPSIS
+--------
+[verse]
+'git diff-blob' <blob> <blob>
+
+DESCRIPTION
+-----------
+Compare the content and mode of two specified blobs.
+
+OPTIONS
+-------
+<blob>::
+	The id of a blob object or path-scoped revision that resolves to a blob.
+
+include::pretty-formats.txt[]
+
+include::diff-format.txt[]
+
+GIT
+---
+Part of the linkgit:git[1] suite
diff --git a/Documentation/meson.build b/Documentation/meson.build
index f2426ccaa3..1bf0a80419 100644
--- a/Documentation/meson.build
+++ b/Documentation/meson.build
@@ -39,6 +39,7 @@ manpages = {
   'git-daemon.txt' : 1,
   'git-describe.txt' : 1,
   'git-diagnose.txt' : 1,
+  'git-diff-blob.txt' : 1,
   'git-diff-files.txt' : 1,
   'git-diff-index.txt' : 1,
   'git-difftool.txt' : 1,
diff --git a/Makefile b/Makefile
index 06f01149ec..de2e43d4f6 100644
--- a/Makefile
+++ b/Makefile
@@ -1235,6 +1235,7 @@ BUILTIN_OBJS += builtin/credential-store.o
 BUILTIN_OBJS += builtin/credential.o
 BUILTIN_OBJS += builtin/describe.o
 BUILTIN_OBJS += builtin/diagnose.o
+BUILTIN_OBJS += builtin/diff-blob.o
 BUILTIN_OBJS += builtin/diff-files.o
 BUILTIN_OBJS += builtin/diff-index.o
 BUILTIN_OBJS += builtin/diff-tree.o
diff --git a/builtin.h b/builtin.h
index f7b166b334..383e78ca99 100644
--- a/builtin.h
+++ b/builtin.h
@@ -152,6 +152,7 @@ int cmd_diagnose(int argc, const char **argv, const char *prefix, struct reposit
 int cmd_diff_files(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_diff_index(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_diff(int argc, const char **argv, const char *prefix, struct repository *repo);
+int cmd_diff_blob(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_diff_tree(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_difftool(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_env__helper(int argc, const char **argv, const char *prefix, struct repository *repo);
diff --git a/builtin/diff-blob.c b/builtin/diff-blob.c
new file mode 100644
index 0000000000..7cfa4eb436
--- /dev/null
+++ b/builtin/diff-blob.c
@@ -0,0 +1,117 @@
+#include "builtin.h"
+#include "config.h"
+#include "diff.h"
+#include "diffcore.h"
+#include "gettext.h"
+#include "hash.h"
+#include "object.h"
+#include "parse-options.h"
+#include "revision.h"
+
+static void diff_blobs(struct object_array_entry *old_blob,
+		       struct object_array_entry *new_blob,
+		       struct diff_options *opts)
+{
+	const unsigned mode = canon_mode(S_IFREG | 0644);
+	struct object_id old_oid = old_blob->item->oid;
+	struct object_id new_oid = new_blob->item->oid;
+	unsigned old_mode = old_blob->mode;
+	unsigned new_mode = new_blob->mode;
+	char *old_path = old_blob->path;
+	char *new_path = new_blob->path;
+	struct diff_filespec *old, *new;
+
+	if (old_mode == S_IFINVALID)
+		old_mode = mode;
+
+	if (new_mode == S_IFINVALID)
+		new_mode = mode;
+
+	if (!old_path)
+		old_path = old_blob->name;
+
+	if (!new_path)
+		new_path = new_blob->name;
+
+	if (!is_null_oid(&old_oid) && !is_null_oid(&new_oid) &&
+	    oideq(&old_oid, &new_oid) && (old_mode == new_mode))
+		return;
+
+	if (opts->flags.reverse_diff) {
+		SWAP(old_oid, new_oid);
+		SWAP(old_mode, new_mode);
+		SWAP(old_path, new_path);
+	}
+
+	if (opts->prefix &&
+	    (strncmp(old_path, opts->prefix, opts->prefix_length) ||
+	     strncmp(new_path, opts->prefix, opts->prefix_length)))
+		return;
+
+	old = alloc_filespec(old_path);
+	new = alloc_filespec(new_path);
+
+	fill_filespec(old, &old_oid, 1, old_mode);
+	fill_filespec(new, &new_oid, 1, new_mode);
+
+	diff_queue(&diff_queued_diff, old, new);
+	diffcore_std(opts);
+	diff_flush(opts);
+}
+
+int cmd_diff_blob(int argc, const char **argv, const char *prefix,
+		  struct repository *repo)
+{
+	struct object_array_entry *old_blob, *new_blob;
+	struct rev_info revs;
+	int ret;
+
+	const char * const usage[] = {
+		N_("git diff-blob <blob> <blob>"),
+		NULL
+	};
+	struct option options[] = {
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, usage,
+			     PARSE_OPT_KEEP_UNKNOWN_OPT | PARSE_OPT_KEEP_ARGV0);
+
+	repo_config(repo, git_diff_basic_config, NULL);
+	prepare_repo_settings(repo);
+	repo->settings.command_requires_full_index = 0;
+
+	repo_init_revisions(repo, &revs, prefix);
+	revs.abbrev = 0;
+	revs.diff = 1;
+	revs.disable_stdin = 1;
+
+	prefix = precompose_argv_prefix(argc, argv, prefix);
+	argc = setup_revisions(argc, argv, &revs, NULL);
+
+	if (!revs.diffopt.output_format)
+		revs.diffopt.output_format = DIFF_FORMAT_PATCH;
+
+	switch (revs.pending.nr) {
+	case 2:
+		old_blob = &revs.pending.objects[0];
+		new_blob = &revs.pending.objects[1];
+
+		if (old_blob->item->type != OBJ_BLOB)
+			die("object %s is not a blob", old_blob->name);
+
+		if (new_blob->item->type != OBJ_BLOB)
+			die("object %s is not a blob", new_blob->name);
+
+		diff_blobs(old_blob, new_blob, &revs.diffopt);
+
+		break;
+	default:
+		usage_with_options(usage, options);
+	}
+
+	ret = diff_result_code(&revs);
+	release_revisions(&revs);
+
+	return ret;
+}
diff --git a/command-list.txt b/command-list.txt
index e0bb87b3b5..78d8308352 100644
--- a/command-list.txt
+++ b/command-list.txt
@@ -93,6 +93,7 @@ git-daemon                              synchingrepositories
 git-describe                            mainporcelain
 git-diagnose                            ancillaryinterrogators
 git-diff                                mainporcelain           info
+git-diff-blob                           plumbinginterrogators
 git-diff-files                          plumbinginterrogators
 git-diff-index                          plumbinginterrogators
 git-diff-tree                           plumbinginterrogators
diff --git a/git.c b/git.c
index 46b3c740c5..17c018ea36 100644
--- a/git.c
+++ b/git.c
@@ -540,6 +540,7 @@ static struct cmd_struct commands[] = {
 	{ "describe", cmd_describe, RUN_SETUP },
 	{ "diagnose", cmd_diagnose, RUN_SETUP_GENTLY },
 	{ "diff", cmd_diff, NO_PARSEOPT },
+	{ "diff-blob", cmd_diff_blob, RUN_SETUP | NO_PARSEOPT },
 	{ "diff-files", cmd_diff_files, RUN_SETUP | NEED_WORK_TREE | NO_PARSEOPT },
 	{ "diff-index", cmd_diff_index, RUN_SETUP | NO_PARSEOPT },
 	{ "diff-tree", cmd_diff_tree, RUN_SETUP | NO_PARSEOPT },
diff --git a/meson.build b/meson.build
index 0dccebcdf1..fefb802c27 100644
--- a/meson.build
+++ b/meson.build
@@ -503,6 +503,7 @@ builtin_sources = [
   'builtin/credential.c',
   'builtin/describe.c',
   'builtin/diagnose.c',
+  'builtin/diff-blob.c',
   'builtin/diff-files.c',
   'builtin/diff-index.c',
   'builtin/diff-tree.c',
diff --git a/t/t4063-diff-blobs.sh b/t/t4063-diff-blobs.sh
index 50fdb5ea52..23615565fe 100755
--- a/t/t4063-diff-blobs.sh
+++ b/t/t4063-diff-blobs.sh
@@ -1,12 +1,14 @@
 #!/bin/sh
 
-test_description='test direct comparison of blobs via git-diff'
+test_description='test direct comparison of blobs via git-diff and git-diff-blob'
 
 . ./test-lib.sh
 
+commands="diff diff-blob"
+
 run_diff () {
 	# use full-index to make it easy to match the index line
-	git diff --full-index "$@" >diff
+	git $1 --full-index $2 $3 >diff
 }
 
 check_index () {
@@ -37,61 +39,63 @@ test_expect_success 'create some blobs' '
 	sha1_two=$(git rev-parse HEAD:two)
 '
 
-test_expect_success 'diff by sha1' '
-	run_diff $sha1_one $sha1_two
-'
-test_expect_success 'index of sha1 diff' '
-	check_index $sha1_one $sha1_two
-'
-test_expect_success 'sha1 diff uses arguments as paths' '
-	check_paths $sha1_one $sha1_two
-'
-test_expect_success 'sha1 diff has no mode change' '
-	! grep mode diff
-'
-
-test_expect_success 'diff by tree:path (run)' '
-	run_diff HEAD:one HEAD:two
-'
-test_expect_success 'index of tree:path diff' '
-	check_index $sha1_one $sha1_two
-'
-test_expect_success 'tree:path diff uses filenames as paths' '
-	check_paths one two
-'
-test_expect_success 'tree:path diff shows mode change' '
-	check_mode 100644 100755
-'
-
-test_expect_success 'diff by ranged tree:path' '
-	run_diff HEAD:one..HEAD:two
-'
-test_expect_success 'index of ranged tree:path diff' '
-	check_index $sha1_one $sha1_two
-'
-test_expect_success 'ranged tree:path diff uses filenames as paths' '
-	check_paths one two
-'
-test_expect_success 'ranged tree:path diff shows mode change' '
-	check_mode 100644 100755
-'
-
-test_expect_success 'diff blob against file' '
-	run_diff HEAD:one two
+test_expect_success 'diff blob against file (git-diff)' '
+	run_diff diff HEAD:one two
 '
-test_expect_success 'index of blob-file diff' '
+test_expect_success 'index of blob-file diff (git-diff)' '
 	check_index $sha1_one $sha1_two
 '
-test_expect_success 'blob-file diff uses filename as paths' '
+test_expect_success 'blob-file diff uses filename as paths (git-diff)' '
 	check_paths one two
 '
-test_expect_success FILEMODE 'blob-file diff shows mode change' '
+test_expect_success FILEMODE 'blob-file diff shows mode change (git-diff)' '
 	check_mode 100644 100755
 '
 
-test_expect_success 'blob-file diff prefers filename to sha1' '
-	run_diff $sha1_one two &&
+test_expect_success 'blob-file diff prefers filename to sha1 (git-diff)' '
+	run_diff diff $sha1_one two &&
 	check_paths two two
 '
 
+for cmd in $commands; do
+	test_expect_success "diff by sha1 (git-$cmd)" '
+		run_diff $cmd $sha1_one $sha1_two
+	'
+	test_expect_success "index of sha1 diff (git-$cmd)" '
+		check_index $sha1_one $sha1_two
+	'
+	test_expect_success "sha1 diff uses arguments as paths (git-$cmd)" '
+		check_paths $sha1_one $sha1_two
+	'
+	test_expect_success "sha1 diff has no mode change (git-$cmd)" '
+		! grep mode diff
+	'
+
+	test_expect_success "diff by tree:path (run) (git-$cmd)" '
+		run_diff $cmd HEAD:one HEAD:two
+	'
+	test_expect_success "index of tree:path diff (git-$cmd)" '
+		check_index $sha1_one $sha1_two
+	'
+	test_expect_success "tree:path diff uses filenames as paths (git-$cmd)" '
+		check_paths one two
+	'
+	test_expect_success "tree:path diff shows mode change (git-$cmd)" '
+		check_mode 100644 100755
+	'
+
+	test_expect_success "diff by ranged tree:path (git-$cmd)" '
+		run_diff $cmd HEAD:one..HEAD:two
+	'
+	test_expect_success "index of ranged tree:path diff (git-$cmd)" '
+		check_index $sha1_one $sha1_two
+	'
+	test_expect_success "ranged tree:path diff uses filenames as paths (git-$cmd)" '
+		check_paths one two
+	'
+	test_expect_success "ranged tree:path diff shows mode change (git-$cmd)" '
+		check_mode 100644 100755
+	'
+done
+
 test_done

-- 
2.47.1
Previous: Justin ToblerNext: Justin Tobler
Message 2 of 78 in “batch blob diff generation”
  1. 0/3 batch blob diff generationJustin Tobler, Dec 13, 2024
  2. 1/3 builtin: introduce diff-blob commandJustin Tobler, Dec 13, 2024
  3. 2/3 builtin/diff-blob: add "--stdin" optionJustin Tobler, Dec 13, 2024
  4. 3/3 builtin/diff-blob: Add "-z" optionJustin Tobler, Dec 13, 2024
  5. Jeff KingDec 13, 2024
  6. Junio C HamanoDec 13, 2024
  7. Jeff KingDec 13, 2024
  8. Junio C HamanoDec 15, 2024
  9. Junio C HamanoDec 15, 2024
  10. Jeff KingDec 16, 2024
  11. Junio C HamanoDec 16, 2024
  12. Jeff KingDec 18, 2024
  13. Junio C HamanoDec 18, 2024
  14. Jeff KingDec 20, 2024
  15. Jeff KingDec 20, 2024
  16. Justin ToblerDec 13, 2024
  17. Jeff KingDec 16, 2024
  18. Junio C HamanoDec 13, 2024
  19. Junio C HamanoDec 15, 2024
  20. Jeff KingDec 16, 2024
  21. 0/3 batch blob diff generationJustin Tobler, Feb 12, 2025
  22. 1/3 diff: return diff_filepair from diff queue helpersJustin Tobler, Feb 12, 2025
  23. Karthik NayakFeb 12, 2025
  24. Justin ToblerFeb 12, 2025
  25. Patrick SteinhardtFeb 12, 2025
  26. Justin ToblerFeb 12, 2025
  27. Patrick SteinhardtFeb 13, 2025
  28. 2/3 builtin: introduce diff-pairs commandJustin Tobler, Feb 12, 2025
  29. Patrick SteinhardtFeb 12, 2025
  30. Karthik NayakFeb 12, 2025
  31. Justin ToblerFeb 25, 2025
  32. Jean-Noël AvilaFeb 12, 2025
  33. Junio C HamanoFeb 12, 2025
  34. Justin ToblerFeb 19, 2025
  35. Junio C HamanoFeb 19, 2025
  36. Junio C HamanoFeb 19, 2025
  37. Justin ToblerFeb 20, 2025
  38. Justin ToblerFeb 20, 2025
  39. Junio C HamanoFeb 20, 2025
  40. Phillip WoodFeb 17, 2025
  41. Justin ToblerFeb 19, 2025
  42. Junio C HamanoFeb 19, 2025
  43. Justin ToblerFeb 19, 2025
  44. Phillip WoodFeb 26, 2025
  45. 3/3 builtin/diff-pairs: allow explicit diff queue flushJustin Tobler, Feb 12, 2025
  46. Patrick SteinhardtFeb 12, 2025
  47. Phillip WoodFeb 17, 2025
  48. Justin ToblerFeb 19, 2025
  49. 0/3 batch blob diff generationJustin Tobler, Feb 25, 2025
  50. 1/3 diff: return diff_filepair from diff queue helpersJustin Tobler, Feb 25, 2025
  51. Junio C HamanoFeb 26, 2025
  52. 2/3 builtin: introduce diff-pairs commandJustin Tobler, Feb 25, 2025
  53. Junio C HamanoFeb 26, 2025
  54. Justin ToblerFeb 27, 2025
  55. Karthik NayakFeb 27, 2025
  56. Justin ToblerFeb 27, 2025
  57. Patrick SteinhardtFeb 27, 2025
  58. Justin ToblerFeb 27, 2025
  59. 3/3 builtin/diff-pairs: allow explicit diff queue flushJustin Tobler, Feb 25, 2025
  60. phillip.wood123@gmail.comFeb 26, 2025
  61. Justin ToblerFeb 27, 2025
  62. 0/4 batch blob diff generationJustin Tobler, Feb 28, 2025
  63. 1/4 diff: return diff_filepair from diff queue helpersJustin Tobler, Feb 28, 2025
  64. 2/4 diff: add option to skip resolving diff statusesJustin Tobler, Feb 28, 2025
  65. Patrick SteinhardtFeb 28, 2025
  66. Justin ToblerFeb 28, 2025
  67. 3/4 builtin: introduce diff-pairs commandJustin Tobler, Feb 28, 2025
  68. Patrick SteinhardtFeb 28, 2025
  69. Justin ToblerFeb 28, 2025
  70. 4/4 builtin/diff-pairs: allow explicit diff queue flushJustin Tobler, Feb 28, 2025
  71. 0/4 batch blob diff generationJustin Tobler, Feb 28, 2025
  72. 1/4 diff: return diff_filepair from diff queue helpersJustin Tobler, Feb 28, 2025
  73. Junio C HamanoMar 3, 2025
  74. 2/4 diff: add option to skip resolving diff statusesJustin Tobler, Feb 28, 2025
  75. Junio C HamanoMar 3, 2025
  76. 3/4 builtin: introduce diff-pairs commandJustin Tobler, Feb 28, 2025
  77. Junio C HamanoMar 3, 2025
  78. 4/4 builtin/diff-pairs: allow explicit diff queue flushJustin Tobler, Feb 28, 2025

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