Subject: [PATCH 1/2] update-index: optionally leave skip-worktree entries alone

From: "Johannes Schindelin via GitGitGadget" <[email-masked]>
Date: Thu, 26 Sep 2019 00:42:31 -0700 (PDT)

From: Johannes Schindelin <[email-masked]>

While `git update-index` mostly ignores paths referring to index entries
whose skip-worktree bit is set, in b4d1690df11 (Teach Git to respect
skip-worktree bit (reading part), 2009-08-20), for reasons that are not
entirely obvious, the `--remove` option was made special: it _does_
remove index entries even if their skip-worktree bit is set.

Seeing as this behavior has been in place for a decade now, it does not
make sense to change it.

However, in preparation for fixing a bug in `git stash` where it
pretends that skip-worktree entries have actually been removed, we need
a mode where `git update-index` leaves all skip-worktree entries alone,
even if the `--remove` option was passed.

Signed-off-by: Johannes Schindelin <[email-masked]>
---
 Documentation/git-update-index.txt | 6 ++++++
 builtin/update-index.c             | 6 +++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/Documentation/git-update-index.txt b/Documentation/git-update-index.txt
index 1c4d146a41..08393445e7 100644
--- a/Documentation/git-update-index.txt
+++ b/Documentation/git-update-index.txt
@@ -16,6 +16,7 @@ SYNOPSIS
 	     [--chmod=(+|-)x]
 	     [--[no-]assume-unchanged]
 	     [--[no-]skip-worktree]
+	     [--[no-]ignore-skip-worktree-entries]
 	     [--[no-]fsmonitor-valid]
 	     [--ignore-submodules]
 	     [--[no-]split-index]
@@ -113,6 +114,11 @@ you will need to handle the situation manually.
 	set and unset the "skip-worktree" bit for the paths. See
 	section "Skip-worktree bit" below for more information.
 
+
+--[no-]ignore-skip-worktree-entries::
+	Do not remove skip-worktree (AKA "index-only") entries even when
+	the `--remove` option was specified.
+
 --[no-]fsmonitor-valid::
 	When one of these flags is specified, the object name recorded
 	for the paths are not updated. Instead, these options
diff --git a/builtin/update-index.c b/builtin/update-index.c
index dff2f4b837..074d563df0 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -35,6 +35,7 @@ static int verbose;
 static int mark_valid_only;
 static int mark_skip_worktree_only;
 static int mark_fsmonitor_only;
+static int ignore_skip_worktree_entries;
 #define MARK_FLAG 1
 #define UNMARK_FLAG 2
 static struct strbuf mtime_dir = STRBUF_INIT;
@@ -381,7 +382,8 @@ static int process_path(const char *path, struct stat *st, int stat_errno)
 		 * so updating it does not make sense.
 		 * On the other hand, removing it from index should work
 		 */
-		if (allow_remove && remove_file_from_cache(path))
+		if (!ignore_skip_worktree_entries && allow_remove &&
+		    remove_file_from_cache(path))
 			return error("%s: cannot remove from the index", path);
 		return 0;
 	}
@@ -1013,6 +1015,8 @@ int cmd_update_index(int argc, const char **argv, const char *prefix)
 		{OPTION_SET_INT, 0, "no-skip-worktree", &mark_skip_worktree_only, NULL,
 			N_("clear skip-worktree bit"),
 			PARSE_OPT_NOARG | PARSE_OPT_NONEG, NULL, UNMARK_FLAG},
+		OPT_BOOL(0, "ignore-skip-worktree-entries", &ignore_skip_worktree_entries,
+			 N_("do not touch index-only entries")),
 		OPT_SET_INT(0, "info-only", &info_only,
 			N_("add to index only; do not add content to object database"), 1),
 		OPT_SET_INT(0, "force-remove", &force_remove,
-- 
gitgitgadget