git/list[1] front-page[2] threads[3] people[4] search[5] about
 

[PATCH 1/1] diffcore: add a filter to find a specific blob

From
Stefan Beller <sbeller@google.com>
Date
Dec 11, 2017, 19:58 UTC
Message-ID
<20171211195835.57057-2-sbeller@google.com>
In-Reply-To
<20171211195835.57057-1-sbeller@google.com>

Sometimes users are given a hash of an object and they want to identify it further (ex.: Use verify-pack to find the largest blobs, but what are these? or [1])

One might be tempted to extend git-describe to also work with blobs, such that `git describe <blob-id>` gives a description as '<commit-ish>:<path>'. This was implemented at [2]; as seen by the sheer number of responses (>110), it turns out this is tricky to get right. The hard part to get right is picking the correct 'commit-ish' as that could be the commit that (re-)introduced the blob or the blob that removed the blob; the blob could exist in different branches.

Junio hinted at a different approach of solving this problem, which this patch implements. Teach the diff machinery another flag for restricting the information to what is shown. For example:

  $ ./git log --oneline --blobfind=v2.0.0:Makefile
  b2feb64309 Revert the whole "ask curl-config" topic for now
  47fbfded53 i18n: only extract comments marked with "TRANSLATORS:"

we observe that the Makefile as shipped with 2.0 was introduced in v1.9.2-471-g47fbfded53 and replaced in v2.0.0-rc1-5-gb2feb64309 by a different blob.

[1] https://stackoverflow.com/questions/223678/which-commit-has-this-blob [2] https://public-inbox.org/git/20171028004419.10139-1-sbeller@google.com/

Signed-off-by: Stefan Beller <sbeller@google.com>
---
 Documentation/diff-options.txt |  6 +++++
 Makefile                       |  1 +
 builtin/log.c                  |  2 +-
 diff.c                         | 21 ++++++++++++++++-
 diff.h                         |  3 +++
 diffcore-oidfind.c             | 42 ++++++++++++++++++++++++++++++++++
 diffcore.h                     |  1 +
 revision.c                     |  5 ++++-
 t/t4064-diff-oidfind.sh        | 51 ++++++++++++++++++++++++++++++++++++++++++
 9 files changed, 129 insertions(+), 3 deletions(-)
 create mode 100644 diffcore-oidfind.c
 create mode 100755 t/t4064-diff-oidfind.sh
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index dd0dba5b1d..67a99e522b 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -500,6 +500,12 @@ information.
 --pickaxe-regex::
 	Treat the <string> given to `-S` as an extended POSIX regular
 	expression to match.
+
+--find-object=<object-id>::
+	Restrict the output such that one side of the diff
+	matches the given object id. The object can be a blob,
+	or gitlink entry.
+
 endif::git-format-patch[]
 
 -O<orderfile>::
diff --git a/Makefile b/Makefile
index ee9d5eb11e..fc2b136694 100644
--- a/Makefile
+++ b/Makefile
@@ -775,6 +775,7 @@ LIB_OBJS += date.o
 LIB_OBJS += decorate.o
 LIB_OBJS += diffcore-break.o
 LIB_OBJS += diffcore-delta.o
+LIB_OBJS += diffcore-oidfind.o
 LIB_OBJS += diffcore-order.o
 LIB_OBJS += diffcore-pickaxe.o
 LIB_OBJS += diffcore-rename.o
diff --git a/builtin/log.c b/builtin/log.c
index 6c1fa896ad..2ab7f338e6 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -181,7 +181,7 @@ static void cmd_log_init_finish(int argc, const char **argv, const char *prefix,
 		init_display_notes(&rev->notes_opt);
 
 	if (rev->diffopt.pickaxe || rev->diffopt.filter ||
-	    rev->diffopt.flags.follow_renames)
+	    rev->diffopt.flags.follow_renames || rev->diffopt.oidfind)
 		rev->always_show_header = 0;
 
 	if (source)
diff --git a/diff.c b/diff.c
index 0763e89263..cb35934634 100644
--- a/diff.c
+++ b/diff.c
@@ -4082,6 +4082,7 @@ void diff_setup(struct diff_options *options)
 	options->interhunkcontext = diff_interhunk_context_default;
 	options->ws_error_highlight = ws_error_highlight_default;
 	options->flags.rename_empty = 1;
+	options->oidfind = NULL;
 
 	/* pathchange left =NULL by default */
 	options->change = diff_change;
@@ -4487,6 +4488,20 @@ static int parse_ws_error_highlight_opt(struct diff_options *opt, const char *ar
 	return 1;
 }
 
+static int parse_oidfind_opt(struct diff_options *opt, const char *arg)
+{
+	struct object_id oid;
+
+	/* We don't even need to have the object, any oid works. */
+	if (get_oid_blob(arg, &oid))
+		return error("unable to resolve '%s'", arg);
+
+	if (!opt->oidfind)
+		opt->oidfind = xcalloc(1, sizeof(*opt->oidfind));
+	oidset_insert(opt->oidfind, &oid);
+	return 1;
+}
+
 int diff_opt_parse(struct diff_options *options,
 		   const char **av, int ac, const char *prefix)
 {
@@ -4736,7 +4751,8 @@ int diff_opt_parse(struct diff_options *options,
 	else if ((argcount = short_opt('O', av, &optarg))) {
 		options->orderfile = prefix_filename(prefix, optarg);
 		return argcount;
-	}
+	} else if (skip_prefix(arg, "--find-object=", &arg))
+		return parse_oidfind_opt(options, arg);
 	else if ((argcount = parse_long_opt("diff-filter", av, &optarg))) {
 		int offending = parse_diff_filter_opt(optarg, options);
 		if (offending)
@@ -5770,6 +5786,9 @@ void diffcore_std(struct diff_options *options)
 		diffcore_skip_stat_unmatch(options);
 	if (!options->found_follow) {
 		/* See try_to_follow_renames() in tree-diff.c */
+
+		if (options->oidfind)
+			diffcore_oidfind(options);
 		if (options->break_opt != -1)
 			diffcore_break(options->break_opt);
 		if (options->detect_rename)
diff --git a/diff.h b/diff.h
index 0fb18dd735..d2badb29a1 100644
--- a/diff.h
+++ b/diff.h
@@ -7,6 +7,7 @@
 #include "tree-walk.h"
 #include "pathspec.h"
 #include "object.h"
+#include "oidset.h"
 
 struct rev_info;
 struct diff_options;
@@ -174,6 +175,8 @@ struct diff_options {
 	enum diff_words_type word_diff;
 	enum diff_submodule_format submodule_format;
 
+	struct oidset *oidfind;
+
 	/* this is set by diffcore for DIFF_FORMAT_PATCH */
 	int found_changes;
 
diff --git a/diffcore-oidfind.c b/diffcore-oidfind.c
new file mode 100644
index 0000000000..39a0b5390f
--- /dev/null
+++ b/diffcore-oidfind.c
@@ -0,0 +1,42 @@
+/*
+ * Copyright (c) 2017 Google Inc.
+ */
+#include "cache.h"
+#include "diff.h"
+#include "diffcore.h"
+
+static void diffcore_filter_blobs(struct diff_queue_struct *q,
+				  struct diff_options *options)
+{
+	int src, dst;
+
+	if (!options->oidfind)
+		BUG("oidfind oidset not initialized???");
+
+	for (src = dst = 0; src < q->nr; src++) {
+		struct diff_filepair *p = q->queue[src];
+
+		if (!DIFF_PAIR_UNMERGED(p) &&
+		    ((DIFF_FILE_VALID(p->one) &&
+		     oidset_contains(options->oidfind, &p->one->oid)) ||
+		    (DIFF_FILE_VALID(p->two) &&
+		     oidset_contains(options->oidfind, &p->two->oid)))) {
+			q->queue[dst] = p;
+			dst++;
+		} else {
+			diff_free_filepair(p);
+		}
+	}
+
+	if (!dst) {
+		free(q->queue);
+		DIFF_QUEUE_CLEAR(q);
+	} else {
+		q->nr = dst;
+	}
+}
+
+void diffcore_oidfind(struct diff_options *options)
+{
+	diffcore_filter_blobs(&diff_queued_diff, options);
+}
diff --git a/diffcore.h b/diffcore.h
index a30da161da..6bb1d76b1a 100644
--- a/diffcore.h
+++ b/diffcore.h
@@ -107,6 +107,7 @@ extern struct diff_filepair *diff_queue(struct diff_queue_struct *,
 					struct diff_filespec *);
 extern void diff_q(struct diff_queue_struct *, struct diff_filepair *);
 
+extern void diffcore_oidfind(struct diff_options *);
 extern void diffcore_break(int);
 extern void diffcore_rename(struct diff_options *);
 extern void diffcore_merge_broken(void);
diff --git a/revision.c b/revision.c
index e2e691dd5a..e4611054b9 100644
--- a/revision.c
+++ b/revision.c
@@ -2409,7 +2409,8 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
 	/* Pickaxe, diff-filter and rename following need diffs */
 	if (revs->diffopt.pickaxe ||
 	    revs->diffopt.filter ||
-	    revs->diffopt.flags.follow_renames)
+	    revs->diffopt.flags.follow_renames ||
+	    revs->diffopt.oidfind)
 		revs->diff = 1;
 
 	if (revs->topo_order)
@@ -2883,6 +2884,8 @@ int prepare_revision_walk(struct rev_info *revs)
 		simplify_merges(revs);
 	if (revs->children.name)
 		set_children(revs);
+	if (revs->diffopt.oidfind)
+		revs->simplify_history = 0;
 	return 0;
 }
 
diff --git a/t/t4064-diff-oidfind.sh b/t/t4064-diff-oidfind.sh
new file mode 100755
index 0000000000..7afe62df87
--- /dev/null
+++ b/t/t4064-diff-oidfind.sh
@@ -0,0 +1,51 @@
+#!/bin/sh
+
+test_description='test finding specific blobs in the revision walking'
+. ./test-lib.sh
+
+test_expect_success 'setup ' '
+	git commit --allow-empty -m "empty initial commit" &&
+
+	echo "Hello, world!" >greeting &&
+	git add greeting &&
+	git commit -m "add the greeting blob" && # borrowed from Git from the Bottom Up
+	git tag -m "the blob" greeting $(git rev-parse HEAD:greeting) &&
+
+	echo asdf >unrelated &&
+	git add unrelated &&
+	git commit -m "unrelated history" &&
+
+	git revert HEAD^ &&
+
+	git commit --allow-empty -m "another unrelated commit"
+'
+
+test_expect_success 'find the greeting blob' '
+	cat >expect <<-EOF &&
+	Revert "add the greeting blob"
+	add the greeting blob
+	EOF
+
+	git log --format=%s --find-object=greeting^{blob} >actual &&
+
+	test_cmp expect actual
+'
+
+test_expect_success 'setup a submodule' '
+	test_create_repo sub &&
+	test_commit -C sub sub &&
+	git submodule add ./sub sub &&
+	git commit -a -m "add sub"
+'
+
+test_expect_success 'find a submodule' '
+	cat >expect <<-EOF &&
+	add sub
+	EOF
+
+	git log --format=%s --find-object=HEAD:sub >actual &&
+
+	test_cmp expect actual
+'
+
+test_done

-- 
2.15.1.424.g9478a66081-goog
Previous: Stefan BellerNext: Junio C Hamano
Message 13 of 25 in “diffcore-blobfind”
  1. 0/1 diffcore-blobfindStefan Beller, Dec 8, 2017
  2. 1/1 diffcore: add a filter to find a specific blobStefan Beller, Dec 8, 2017
  3. Jeff KingDec 8, 2017
  4. Ramsay JonesDec 8, 2017
  5. Jeff KingDec 8, 2017
  6. Stefan BellerDec 8, 2017
  7. Jeff KingDec 8, 2017
  8. Junio C HamanoDec 8, 2017
  9. Junio C HamanoDec 8, 2017
  10. Stefan BellerDec 8, 2017
  11. Junio C HamanoDec 8, 2017
  12. 0/1 diff-core blobfindStefan Beller, Dec 11, 2017
  13. 1/1 diffcore: add a filter to find a specific blobStefan Beller, Dec 11, 2017
  14. Junio C HamanoDec 11, 2017
  15. Stefan BellerDec 12, 2017
  16. diffcore: add a filter to find a specific blobStefan Beller, Dec 12, 2017
  17. Junio C HamanoDec 12, 2017
  18. Jonathan NiederDec 14, 2017
  19. Stefan BellerDec 14, 2017
  20. Jonathan NiederDec 14, 2017
  21. Junio C HamanoDec 15, 2017
  22. Stefan BellerDec 27, 2017
  23. Jonathan NiederDec 27, 2017
  24. Junio C HamanoDec 27, 2017
  25. Junio C HamanoDec 14, 2017

Read the whole thread, see it on lore, or plain text.

$ cat FOOTERMessages come from the public archive at lore.kernel.org/git, fetched every hour. The front page is chosen and written each morning by an AI editor and can be wrong; the threads themselves are the record. About and API. For agents: an MCP server at https://gitlist.dev/mcp, and any thread, story or person page as Markdown by adding .md to its URL (or sending Accept: text/markdown). Details in /llms.txt.