[PATCH v3 2/2] reflog: implement subcommand to drop reflogs

[Karthik Nayak <karthik.188@gmail.com>]

While 'git-reflog(1)' currently allows users to expire reflogs and
delete individual entries, it lacks functionality to completely remove
reflogs for specific references. This becomes problematic in
repositories where reflogs are not needed but continue to accumulate
entries despite setting 'core.logAllRefUpdates=false'.

Add a new 'drop' subcommand to git-reflog that allows users to delete
the entire reflog for a specified reference. Include an '--all' flag to
enable dropping all reflogs from all worktrees and an addon flag
'--single-worktree', to only drop all reflogs from the current worktree.

While here, remove an extraneous newline in the file.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
---
 Documentation/git-reflog.adoc |  23 ++++++--
 builtin/reflog.c              |  66 ++++++++++++++++++++++-
 t/t1410-reflog.sh             | 122 ++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 206 insertions(+), 5 deletions(-)

diff --git a/Documentation/git-reflog.adoc b/Documentation/git-reflog.adoc
index a929c52982..b55c060569 100644
--- a/Documentation/git-reflog.adoc
+++ b/Documentation/git-reflog.adoc
@@ -16,6 +16,7 @@ SYNOPSIS
 	[--dry-run | -n] [--verbose] [--all [--single-worktree] | <refs>...]
 'git reflog delete' [--rewrite] [--updateref]
 	[--dry-run | -n] [--verbose] <ref>@{<specifier>}...
+'git reflog drop' [--all [--single-worktree] | <refs>...]
 'git reflog exists' <ref>
 
 DESCRIPTION
@@ -48,10 +49,14 @@ and not reachable from the current tip, are removed from the reflog.
 This is typically not used directly by end users -- instead, see
 linkgit:git-gc[1].
 
-The "delete" subcommand deletes single entries from the reflog. Its
-argument must be an _exact_ entry (e.g. "`git reflog delete
-master@{2}`"). This subcommand is also typically not used directly by
-end users.
+The "delete" subcommand deletes single entries from the reflog, but
+not the reflog itself. Its argument must be an _exact_ entry (e.g. "`git
+reflog delete master@{2}`"). This subcommand is also typically not used
+directly by end users.
+
+The "drop" subcommand completely removes the reflog for the specified
+references. This is in contrast to "expire" and "delete", both of which
+can be used to delete reflog entries, but not the reflog itself.
 
 The "exists" subcommand checks whether a ref has a reflog.  It exits
 with zero status if the reflog exists, and non-zero status if it does
@@ -132,6 +137,16 @@ Options for `delete`
 `--dry-run`, and `--verbose`, with the same meanings as when they are
 used with `expire`.
 
+Options for `drop`
+~~~~~~~~~~~~~~~~~~~~
+
+--all::
+	Drop the reflogs of all references from all worktrees.
+
+--single-worktree::
+	By default when `--all` is specified, reflogs from all working
+	trees are dropped. This option limits the processing to reflogs
+	from the current working tree only.
 
 GIT
 ---
diff --git a/builtin/reflog.c b/builtin/reflog.c
index 762719315e..a3652e69f1 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c
@@ -29,6 +29,9 @@
 #define BUILTIN_REFLOG_EXISTS_USAGE \
 	N_("git reflog exists <ref>")
 
+#define BUILTIN_REFLOG_DROP_USAGE \
+	N_("git reflog drop [--all [--single-worktree] | <refs>...]")
+
 static const char *const reflog_show_usage[] = {
 	BUILTIN_REFLOG_SHOW_USAGE,
 	NULL,
@@ -54,11 +57,17 @@ static const char *const reflog_exists_usage[] = {
 	NULL,
 };
 
+static const char *const reflog_drop_usage[] = {
+	BUILTIN_REFLOG_DROP_USAGE,
+	NULL,
+};
+
 static const char *const reflog_usage[] = {
 	BUILTIN_REFLOG_SHOW_USAGE,
 	BUILTIN_REFLOG_LIST_USAGE,
 	BUILTIN_REFLOG_EXPIRE_USAGE,
 	BUILTIN_REFLOG_DELETE_USAGE,
+	BUILTIN_REFLOG_DROP_USAGE,
 	BUILTIN_REFLOG_EXISTS_USAGE,
 	NULL
 };
@@ -449,10 +458,64 @@ static int cmd_reflog_exists(int argc, const char **argv, const char *prefix,
 				   refname);
 }
 
+static int cmd_reflog_drop(int argc, const char **argv, const char *prefix,
+			   struct repository *repo)
+{
+	int ret = 0, do_all = 0, single_worktree = 0;
+	const struct option options[] = {
+		OPT_BOOL(0, "all", &do_all, N_("drop the reflogs of all references")),
+		OPT_BOOL(0, "single-worktree", &single_worktree,
+			 N_("drop reflogs from the current worktree only")),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, reflog_drop_usage, 0);
+
+	if (argc && do_all)
+		usage(_("references specified along with --all"));
+
+	if (do_all) {
+		struct worktree_reflogs collected = {
+			.reflogs = STRING_LIST_INIT_DUP,
+		};
+		struct string_list_item *item;
+		struct worktree **worktrees, **p;
+
+		worktrees = get_worktrees();
+		for (p = worktrees; *p; p++) {
+			if (single_worktree && !(*p)->is_current)
+				continue;
+			collected.worktree = *p;
+			refs_for_each_reflog(get_worktree_ref_store(*p),
+					     collect_reflog, &collected);
+		}
+		free_worktrees(worktrees);
+
+		for_each_string_list_item(item, &collected.reflogs)
+			ret |= refs_delete_reflog(get_main_ref_store(repo),
+						     item->string);
+		string_list_clear(&collected.reflogs, 0);
+
+		return ret;
+	}
+
+	for (int i = 0; i < argc; i++) {
+		char *ref;
+		if (!repo_dwim_log(repo, argv[i], strlen(argv[i]), NULL, &ref)) {
+			ret |= error(_("reflog could not be found: '%s'"), argv[i]);
+			continue;
+		}
+
+		ret |= refs_delete_reflog(get_main_ref_store(repo), ref);
+		free(ref);
+	}
+
+	return ret;
+}
+
 /*
  * main "reflog"
  */
-
 int cmd_reflog(int argc,
 	       const char **argv,
 	       const char *prefix,
@@ -465,6 +528,7 @@ int cmd_reflog(int argc,
 		OPT_SUBCOMMAND("expire", &fn, cmd_reflog_expire),
 		OPT_SUBCOMMAND("delete", &fn, cmd_reflog_delete),
 		OPT_SUBCOMMAND("exists", &fn, cmd_reflog_exists),
+		OPT_SUBCOMMAND("drop", &fn, cmd_reflog_drop),
 		OPT_END()
 	};
 
diff --git a/t/t1410-reflog.sh b/t/t1410-reflog.sh
index 1f7249be76..42b501f163 100755
--- a/t/t1410-reflog.sh
+++ b/t/t1410-reflog.sh
@@ -551,4 +551,126 @@ test_expect_success 'reflog with invalid object ID can be listed' '
 	)
 '
 
+test_expect_success 'reflog drop non-existent ref' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_must_fail git reflog exists refs/heads/non-existent &&
+		test_must_fail git reflog drop refs/heads/non-existent 2>stderr &&
+		test_grep "error: reflog could not be found: ${SQ}refs/heads/non-existent${SQ}" stderr
+	)
+'
+
+test_expect_success 'reflog drop' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		test_commit_bulk --ref=refs/heads/branch 1 &&
+		git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/branch &&
+		git reflog drop refs/heads/main &&
+		test_must_fail git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/branch
+	)
+'
+
+test_expect_success 'reflog drop multiple references' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		test_commit_bulk --ref=refs/heads/branch 1 &&
+		git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/branch &&
+		git reflog drop refs/heads/main refs/heads/branch &&
+		test_must_fail git reflog exists refs/heads/main &&
+		test_must_fail git reflog exists refs/heads/branch
+	)
+'
+
+test_expect_success 'reflog drop multiple references some non-existent' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		test_commit_bulk --ref=refs/heads/branch 1 &&
+		git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/branch &&
+		test_must_fail git reflog exists refs/heads/non-existent &&
+		test_must_fail git reflog drop refs/heads/main refs/heads/non-existent refs/heads/branch 2>stderr &&
+		test_must_fail git reflog exists refs/heads/main &&
+		test_must_fail git reflog exists refs/heads/branch &&
+		test_must_fail git reflog exists refs/heads/non-existent &&
+		test_grep "error: reflog could not be found: ${SQ}refs/heads/non-existent${SQ}" stderr
+	)
+'
+
+test_expect_success 'reflog drop --all' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		test_commit_bulk --ref=refs/heads/branch 1 &&
+		git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/branch &&
+		git reflog drop --all &&
+		test_must_fail git reflog exists refs/heads/main &&
+		test_must_fail git reflog exists refs/heads/branch
+	)
+'
+
+test_expect_success 'reflog drop --all multiple worktrees' '
+	test_when_finished "rm -rf repo" &&
+	test_when_finished "rm -rf wt" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		git worktree add ../wt &&
+		test_commit_bulk -C ../wt --ref=refs/heads/branch 1 &&
+		git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/branch &&
+		git reflog drop --all &&
+		test_must_fail git reflog exists refs/heads/main &&
+		test_must_fail git reflog exists refs/heads/branch
+	)
+'
+
+test_expect_success 'reflog drop --all --single-worktree' '
+	test_when_finished "rm -rf repo" &&
+	test_when_finished "rm -rf wt" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		git worktree add ../wt &&
+		test_commit -C ../wt foobar &&
+		git reflog exists refs/heads/main &&
+		git reflog exists refs/heads/wt &&
+		test-tool ref-store worktree:wt reflog-exists HEAD &&
+		git reflog drop --all --single-worktree &&
+		test_must_fail git reflog exists refs/heads/main &&
+		test_must_fail git reflog exists refs/heads/wt &&
+		test_must_fail test-tool ref-store worktree:main reflog-exists HEAD &&
+		test-tool ref-store worktree:wt reflog-exists HEAD
+	)
+'
+
+test_expect_success 'reflog drop --all with reference' '
+	test_when_finished "rm -rf repo" &&
+	git init repo &&
+	(
+		cd repo &&
+		test_commit A &&
+		test_must_fail git reflog drop --all refs/heads/main 2>stderr &&
+		test_grep "usage: references specified along with --all" stderr
+	)
+'
+
 test_done

-- 
2.48.1