Patrick Steinhardt [off-list ref] writes:

On Fri, Mar 07, 2025 at 12:17:26PM +0100, Karthik Nayak wrote:

quoted

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 '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'.

I think the order of the two paragraphs should be switched: we tend to
first explain the problem before explaining how to address it.

That makes sense, let me do that.

quoted

While here, remove an erranous newline in the file.

I suspet this should either be "extraneous" or "erroneous"? I cannot
quite tell which of both it shuld be :)

I was thinking similar but decided to go with the latter (sans typo).
Will fix it.

quoted

Signed-off-by: Karthik Nayak <redacted>
---
 Documentation/git-reflog.adoc |  6 +++++
 builtin/reflog.c              | 58 ++++++++++++++++++++++++++++++++++++++++++-
 t/t1410-reflog.sh             | 55 ++++++++++++++++++++++++++++++++++++++++
 3 files changed, 118 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-reflog.adoc b/Documentation/git-reflog.adoc
index a929c52982..4ecee297de 100644
--- a/Documentation/git-reflog.adoc
+++ b/Documentation/git-reflog.adoc

@@ -17,6 +17,7 @@ SYNOPSIS
 'git reflog delete' [--rewrite] [--updateref]
 	[--dry-run | -n] [--verbose] <ref>@{<specifier>}...
 'git reflog exists' <ref>
+'git reflog drop' [--all | <refs>...]

Should we put the command next to `delete`?

I would have like it if they were actually alphabetically sorted, but I
guess this is good alternative to cluster similar sub-commands.

quoted

 DESCRIPTION
 -----------

@@ -57,6 +58,11 @@ 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 removes the reflog for the specified references.
+In contrast, "expire" can be used to prune all entries from a reflog,
+but the reflog itself will still exist for that reference. To fully
+remove the reflog for specific references, use the "drop" subcommand.

The last sentence feels like pointless duplication to me. We should
likely also point out how it is different from "delete". How about:

    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.

It might also be useful to add a comment to "delete" to say that it
deletes entries, but not the reflog.

Thanks, this does look better and I agree, we should call out "delete"
too.

quoted

 OPTIONS
 -------

diff --git a/builtin/reflog.c b/builtin/reflog.c
index f92258f6b6..232602c1a6 100644
--- a/builtin/reflog.c
+++ b/builtin/reflog.c

@@ -27,6 +27,9 @@
 #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,

@@ -52,12 +55,18 @@ 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_EXISTS_USAGE,
+	BUILTIN_REFLOG_DROP_USAGE,
 	NULL
 };

@@ -447,10 +456,56 @@ 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 i, ret, do_all;
+	const struct option options[] = {
+		OPT_BOOL(0, "all", &do_all, N_("process the reflogs of all references")),
+		OPT_END()
+	};
+
+	do_all = ret = 0;

Can't we initiailize the variables directly when declaring them?

We can, let me fix it! I'll also move the initialization of 'i' down to
the loop while we're here.

quoted

+	argc = parse_options(argc, argv, prefix, options, reflog_drop_usage, 0);
+
+	if (do_all) {

`do_all` and `argc > 0` should be mutually exclusive from my point of
view, as the combination does not make any sense. We should likely die
if we see both to be non-zero. Similarly, I think we should abort on
`!do_all && !argc`.

Makes sense, let me add a 'die()' there.

quoted

+		struct worktree_reflogs collected = {
+			.reflogs = STRING_LIST_INIT_DUP,
+		};
+		struct string_list_item *item;
+		struct worktree **worktrees, **p;

Would it be useful to point out in the docs that we also prune logs of
worktrees?

Yes it would, will add.

quoted

+		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 (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;
+		}

Is there a particular reason why we have to double check that the reflog
that we just enumerated really exists? It feels rather unnecessary to
me.

You mean we could directly do `(get_main_ref_store(repo), argv[i]);` ?
The issue is that this returns '0', even when the reflog doesn't exist.
So to notify the user correctly, we do this check.

quoted

diff --git a/t/t1410-reflog.sh b/t/t1410-reflog.sh
index 388fdf9ae5..b6e44ce6b9 100755
--- a/t/t1410-reflog.sh
+++ b/t/t1410-reflog.sh

@@ -551,4 +551,59 @@ 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

Do we want to check the error message of the latter command?

That would be nice addittion, will add.

Patrick