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

[PATCH 6/7] show, log: provide a --remerge-diff capability

From
Elijah Newren via GitGitGadget <gitgitgadget@gmail.com>
Date
Aug 31, 2021, 02:26 UTC
Message-ID
<b75e73384fde4f23296bd02eb40455263f805706.1630376800.git.gitgitgadget@gmail.com>
In-Reply-To
<pull.1080.git.git.1630376800.gitgitgadget@gmail.com>
From: Elijah Newren <newren@gmail.com>

When this option is specified, we remerge all (two parent) merge commits and diff the actual merge commit to the automatically created version, in order to show how users removed conflict markers, resolved the different conflict versions, and potentially added new changes outside of conflict regions in order to resolve semantic merge problems (or, possibly, just to hide other random changes).

This capability works by creating a temporary object directory and marking it as the primary object store, so that any blobs or trees created during the automatic merge, can be easily removed afterwards by just deleting all objects from the temporary object directory. We can do this after handling each merge commit, in order to avoid the need to worry about doing `git gc --auto` runs while running `git log --remerge-diff`.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 builtin/log.c | 23 +++++++++++++++++
 diff-merges.c | 12 +++++++++
 log-tree.c    | 69 +++++++++++++++++++++++++++++++++++++++++++++++++++
 revision.h    |  6 ++++-
 4 files changed, 109 insertions(+), 1 deletion(-)
diff --git a/builtin/log.c b/builtin/log.c
index 3d7717ba5ca..6c7288716e6 100644
--- a/builtin/log.c
+++ b/builtin/log.c
@@ -35,6 +35,8 @@
 #include "repository.h"
 #include "commit-reach.h"
 #include "range-diff.h"
+#include "dir.h"
+#include "tmp-objdir.h"
 
 #define MAIL_DEFAULT_WRAP 72
 #define COVER_FROM_AUTO_MAX_SUBJECT_LEN 100
@@ -51,6 +53,7 @@ static int default_encode_email_headers = 1;
 static int decoration_style;
 static int decoration_given;
 static int use_mailmap_config = 1;
+static struct tmp_objdir *tmp_objdir;
 static const char *fmt_patch_subject_prefix = "PATCH";
 static int fmt_patch_name_max = FORMAT_PATCH_NAME_MAX_DEFAULT;
 static const char *fmt_pretty;
@@ -407,6 +410,17 @@ static int cmd_log_walk(struct rev_info *rev)
 	int saved_nrl = 0;
 	int saved_dcctc = 0;
 
+	if (rev->remerge_diff) {
+		tmp_objdir = tmp_objdir_create();
+		if (!tmp_objdir)
+			die(_("unable to create temporary object directory"));
+		tmp_objdir_make_primary(the_repository, tmp_objdir);
+
+		strbuf_init(&rev->remerge_objdir_location, 0);
+		strbuf_addstr(&rev->remerge_objdir_location,
+			      tmp_objdir_path(tmp_objdir));
+	}
+
 	if (rev->early_output)
 		setup_early_output();
 
@@ -449,6 +463,13 @@ static int cmd_log_walk(struct rev_info *rev)
 	rev->diffopt.no_free = 0;
 	diff_free(&rev->diffopt);
 
+	if (rev->remerge_diff) {
+		strbuf_release(&rev->remerge_objdir_location);
+		tmp_objdir_remove_as_primary(the_repository, tmp_objdir);
+		tmp_objdir_destroy(tmp_objdir);
+		tmp_objdir = NULL;
+	}
+
 	if (rev->diffopt.output_format & DIFF_FORMAT_CHECKDIFF &&
 	    rev->diffopt.flags.check_failed) {
 		return 02;
@@ -1943,6 +1964,8 @@ int cmd_format_patch(int argc, const char **argv, const char *prefix)
 		die(_("--name-status does not make sense"));
 	if (rev.diffopt.output_format & DIFF_FORMAT_CHECKDIFF)
 		die(_("--check does not make sense"));
+	if (rev.remerge_diff)
+		die(_("--remerge_diff does not make sense"));
 
 	if (!use_patch_format &&
 		(!rev.diffopt.output_format ||
diff --git a/diff-merges.c b/diff-merges.c
index d897fd8a293..3a24c45b8e5 100644
--- a/diff-merges.c
+++ b/diff-merges.c
@@ -17,6 +17,7 @@ static void suppress(struct rev_info *revs)
 	revs->combined_all_paths = 0;
 	revs->merges_imply_patch = 0;
 	revs->merges_need_diff = 0;
+	revs->remerge_diff = 0;
 }
 
 static void set_separate(struct rev_info *revs)
@@ -45,6 +46,12 @@ static void set_dense_combined(struct rev_info *revs)
 	revs->dense_combined_merges = 1;
 }
 
+static void set_remerge_diff(struct rev_info *revs)
+{
+	suppress(revs);
+	revs->remerge_diff = 1;
+}
+
 static diff_merges_setup_func_t func_by_opt(const char *optarg)
 {
 	if (!strcmp(optarg, "off") || !strcmp(optarg, "none"))
@@ -57,6 +64,8 @@ static diff_merges_setup_func_t func_by_opt(const char *optarg)
 		return set_combined;
 	else if (!strcmp(optarg, "cc") || !strcmp(optarg, "dense-combined"))
 		return set_dense_combined;
+	else if (!strcmp(optarg, "r") || !strcmp(optarg, "remerge"))
+		return set_remerge_diff;
 	else if (!strcmp(optarg, "m") || !strcmp(optarg, "on"))
 		return set_to_default;
 	return NULL;
@@ -113,6 +122,9 @@ int diff_merges_parse_opts(struct rev_info *revs, const char **argv)
 	} else if (!strcmp(arg, "--cc")) {
 		set_dense_combined(revs);
 		revs->merges_imply_patch = 1;
+	} else if (!strcmp(arg, "--remerge-diff")) {
+		set_remerge_diff(revs);
+		revs->merges_imply_patch = 1;
 	} else if (!strcmp(arg, "--no-diff-merges")) {
 		suppress(revs);
 	} else if (!strcmp(arg, "--combined-all-paths")) {
diff --git a/log-tree.c b/log-tree.c
index 6dc4412268b..ed69a4da140 100644
--- a/log-tree.c
+++ b/log-tree.c
@@ -1,4 +1,5 @@
 #include "cache.h"
+#include "commit-reach.h"
 #include "config.h"
 #include "diff.h"
 #include "object-store.h"
@@ -7,6 +8,7 @@
 #include "tag.h"
 #include "graph.h"
 #include "log-tree.h"
+#include "merge-ort.h"
 #include "reflog-walk.h"
 #include "refs.h"
 #include "string-list.h"
@@ -16,6 +18,7 @@
 #include "line-log.h"
 #include "help.h"
 #include "range-diff.h"
+#include "dir.h"
 
 static struct decoration name_decoration = { "object names" };
 static int decoration_loaded;
@@ -902,6 +905,60 @@ static int do_diff_combined(struct rev_info *opt, struct commit *commit)
 	return !opt->loginfo;
 }
 
+static int do_remerge_diff(struct rev_info *opt,
+			   struct commit_list *parents,
+			   struct object_id *oid,
+			   struct commit *commit)
+{
+	struct merge_options o;
+	struct commit_list *bases;
+	struct merge_result res;
+	struct pretty_print_context ctx = {0};
+	struct strbuf commit1 = STRBUF_INIT;
+	struct strbuf commit2 = STRBUF_INIT;
+
+	/* Setup merge options */
+	init_merge_options(&o, the_repository);
+	memset(&res, 0, sizeof(res));
+	o.show_rename_progress = 0;
+
+	ctx.abbrev = DEFAULT_ABBREV;
+	format_commit_message(parents->item,       "%h (%s)", &commit1, &ctx);
+	format_commit_message(parents->next->item, "%h (%s)", &commit2, &ctx);
+	o.branch1 = commit1.buf;
+	o.branch2 = commit2.buf;
+	o.record_conflict_msgs_in_tree = 1;
+
+	/* Parse the relevant commits and get the merge bases */
+	parse_commit_or_die(parents->item);
+	parse_commit_or_die(parents->next->item);
+	bases = get_merge_bases(parents->item, parents->next->item);
+
+	/* Re-merge the parents */
+	merge_incore_recursive(&o,
+			       bases, parents->item, parents->next->item,
+			       &res);
+
+	/* Show the diff */
+	diff_tree_oid(&res.tree->object.oid, oid, "", &opt->diffopt);
+	log_tree_diff_flush(opt);
+
+	/* Cleanup */
+	strbuf_release(&commit1);
+	strbuf_release(&commit2);
+	merge_finalize(&o, &res);
+
+	/* Clean up the temporary object directory */
+	if (opt->remerge_objdir_location.buf != NULL &&
+	    *opt->remerge_objdir_location.buf != '\0')
+		remove_dir_recursively(&opt->remerge_objdir_location,
+				       REMOVE_DIR_KEEP_TOPLEVEL);
+	else
+		BUG("unable to remove temporary object directory");
+
+	return !opt->loginfo;
+}
+
 /*
  * Show the diff of a commit.
  *
@@ -936,6 +993,18 @@ static int log_tree_diff(struct rev_info *opt, struct commit *commit, struct log
 	}
 
 	if (is_merge) {
+		int octopus = (parents->next->next != NULL);
+
+		if (opt->remerge_diff) {
+			if (octopus) {
+				show_log(opt);
+				fprintf(opt->diffopt.file,
+					"diff: warning: Skipping remerge-diff "
+					"for octopus merges.\n");
+				return 1;
+			}
+			return do_remerge_diff(opt, parents, oid, commit);
+		}
 		if (opt->combine_merges)
 			return do_diff_combined(opt, commit);
 		if (opt->separate_merges) {
diff --git a/revision.h b/revision.h
index fbb068da9fb..d6562c52252 100644
--- a/revision.h
+++ b/revision.h
@@ -198,7 +198,8 @@ struct rev_info {
 			combine_merges:1,
 			combined_all_paths:1,
 			dense_combined_merges:1,
-			first_parent_merges:1;
+			first_parent_merges:1,
+			remerge_diff:1;
 
 	/* Format info */
 	int		show_notes;
@@ -320,6 +321,9 @@ struct rev_info {
 
 	/* misc. flags related to '--no-kept-objects' */
 	unsigned keep_pack_cache_flags;
+
+	/* Location where temporary objects for remerge-diff are written. */
+	struct strbuf remerge_objdir_location;
 };
 
 int ref_excluded(struct string_list *, const char *path);

-- 
gitgitgadget
Previous: Elijah Newren via GitGitGadgetNext: Sergey Organov
Message 54 of 64 in “Add a new --remerge-diff capability to show & log”
  1. 0/7 Add a new --remerge-diff capability to show & logElijah Newren via GitGitGadget, Aug 31, 2021
  2. 1/7 merge-ort: mark a few more conflict messages as omittableElijah Newren via GitGitGadget, Aug 31, 2021
  3. Junio C HamanoAug 31, 2021
  4. Elijah NewrenSep 1, 2021
  5. Junio C HamanoSep 1, 2021
  6. 2/7 merge-ort: add ability to record conflict messages in a fileElijah Newren via GitGitGadget, Aug 31, 2021
  7. Jeff KingSep 28, 2021
  8. Elijah NewrenSep 29, 2021
  9. Junio C HamanoSep 29, 2021
  10. Elijah NewrenSep 29, 2021
  11. Jeff KingSep 30, 2021
  12. Ævar Arnfjörð BjarmasonSep 30, 2021
  13. Elijah NewrenOct 1, 2021
  14. Jeff KingOct 1, 2021
  15. 3/7 ll-merge: add API for capturing warnings in a strbuf instead of stderrElijah Newren via GitGitGadget, Aug 31, 2021
  16. Jeff KingSep 28, 2021
  17. Junio C HamanoSep 28, 2021
  18. Elijah NewrenSep 29, 2021
  19. 4/7 merge-ort: capture and print ll-merge warnings in our preferred fashionElijah Newren via GitGitGadget, Aug 31, 2021
  20. Jeff KingSep 28, 2021
  21. Ævar Arnfjörð BjarmasonSep 30, 2021
  22. Elijah NewrenOct 1, 2021
  23. Ævar Arnfjörð BjarmasonOct 1, 2021
  24. 5/7 tmp-objdir: new API for creating and removing primary object dirsElijah Newren via GitGitGadget, Aug 31, 2021
  25. Ævar Arnfjörð BjarmasonSep 28, 2021
  26. Elijah NewrenSep 29, 2021
  27. Jeff KingSep 30, 2021
  28. Ævar Arnfjörð BjarmasonSep 30, 2021
  29. Elijah NewrenOct 1, 2021
  30. Jeff KingSep 28, 2021
  31. Junio C HamanoSep 29, 2021
  32. Jeff KingSep 30, 2021
  33. Ævar Arnfjörð BjarmasonSep 30, 2021
  34. Jeff KingSep 30, 2021
  35. Elijah NewrenOct 1, 2021
  36. Ævar Arnfjörð BjarmasonOct 1, 2021
  37. Elijah NewrenOct 1, 2021
  38. Elijah NewrenOct 1, 2021
  39. Jeff KingOct 1, 2021
  40. Ævar Arnfjörð BjarmasonOct 1, 2021
  41. Elijah NewrenSep 29, 2021
  42. Jeff KingSep 30, 2021
  43. Jeff KingSep 30, 2021
  44. Junio C HamanoSep 30, 2021
  45. Elijah NewrenOct 1, 2021
  46. Junio C HamanoOct 1, 2021
  47. Elijah NewrenOct 1, 2021
  48. Jeff KingOct 1, 2021
  49. Neeraj SinghSep 30, 2021
  50. Junio C HamanoSep 30, 2021
  51. Junio C HamanoSep 30, 2021
  52. Elijah NewrenOct 1, 2021
  53. 7/7 doc/diff-options: explain the new --remerge-diff optionElijah Newren via GitGitGadget, Aug 31, 2021
  54. 6/7 show, log: provide a --remerge-diff capabilityElijah Newren via GitGitGadget, Aug 31, 2021
  55. Sergey OrganovAug 31, 2021
  56. Ævar Arnfjörð BjarmasonSep 28, 2021
  57. Elijah NewrenSep 29, 2021
  58. Bagas SanjayaAug 31, 2021
  59. Elijah NewrenAug 31, 2021
  60. Junio C HamanoAug 31, 2021
  61. Elijah NewrenAug 31, 2021
  62. Junio C HamanoSep 1, 2021
  63. Elijah NewrenSep 1, 2021
  64. Junio C HamanoSep 1, 2021

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.