reflog: implement subcommand to drop reflogs

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 a '--all' flag to
enable dropping all reflogs in a repository.

While here, remove an extraneous newline in the file.

Signed-off-by: Karthik Nayak <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: KarthikNayak

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 | <refs>...]
 'git reflog exists' <ref>
 
 DESCRIPTION
@@ -48,15 +49,19 @@ 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 "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
 not.
 
+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.
+
 OPTIONS
 -------
 
@@ -132,6 +137,11 @@ 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.
 
 GIT
 ---

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 | <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 +458,58 @@ 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;
+	const struct option options[] = {
+		OPT_BOOL(0, "all", &do_all, N_("process the reflogs of all references")),
+		OPT_END()
+	};
+
+	argc = parse_options(argc, argv, prefix, options, reflog_drop_usage, 0);
+
+	if (argc && do_all)
+		die(_("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++) {
+			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);
+	}
+
+	for (int i = 0; i < argc; i++) {
+		char *ref;
+		if (!repo_dwim_log(repo, argv[i], strlen(argv[i]), NULL, &ref)) {
+			ret |= error(_("%s points nowhere!"), 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 +522,7 @@ 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()
 	};
 

t/t1410-reflog.sh

@@ -551,4 +551,71 @@ 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: refs/heads/non-existent points nowhere!" 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 --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 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 "fatal: references specified along with --all" stderr
+	)
+'
+
 test_done