update-index: add --refresh-stat-only

Documentation/git-update-index.adoc

@@ -109,6 +109,25 @@ you will need to handle the situation manually.
 	Like `--refresh`, but checks stat information unconditionally,
 	without regard to the "assume unchanged" setting.
 
+--refresh-stat-only::
+	Like `--refresh`, but updates only the stat information
+	in the index, without rehashing the file contents. This is
+	useful for large repositories after a working tree has been
+	produced or restored by means other than a normal checkout --
+	for example, a CI cache restore, container provisioning, or
+	copying a working tree from another machine -- when the file
+	contents are known to be correct but the cached stat
+	information no longer matches. Some backup and syncing tools
+	preserve mtimes, but inode numbers, device identifiers, and
+	other filesystem-specific stat fields generally cannot be
+	preserved across machines or even across mounts on the same
+	machine. Like `--really-refresh`, this option disregards the
+	"assume unchanged" setting so that stale stat data on those
+	entries is still updated. Use with care: if the worktree
+	content does not actually match what the index records, the
+	affected entries will appear clean while the recorded object
+	ID remains stale.
+
 --skip-worktree::
 --no-skip-worktree::
 	When one of these flags is specified, the object names recorded

builtin/update-index.c

@@ -766,6 +766,14 @@ static int really_refresh_callback(const struct option *opt,
 	return refresh(opt->value, REFRESH_REALLY);
 }
 
+static int refresh_stat_only_callback(const struct option *opt,
+				const char *arg, int unset)
+{
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+	return refresh(opt->value, REFRESH_STAT_ONLY);
+}
+
 static int chmod_callback(const struct option *opt,
 				const char *arg, int unset)
 {
@@ -957,6 +965,10 @@ int cmd_update_index(int argc,
 			N_("like --refresh, but ignore assume-unchanged setting"),
 			PARSE_OPT_NOARG | PARSE_OPT_NONEG,
 			really_refresh_callback),
+		OPT_CALLBACK_F(0, "refresh-stat-only", &refresh_args, NULL,
+			N_("refresh stat information without checking content"),
+			PARSE_OPT_NOARG | PARSE_OPT_NONEG,
+			refresh_stat_only_callback),
 		{
 			.type = OPTION_LOWLEVEL_CALLBACK,
 			.long_name = "cacheinfo",

preload-index.c

@@ -42,6 +42,7 @@ struct thread_data {
 	struct progress_data *progress;
 	int offset, nr;
 	int t2_nr_lstat;
+	unsigned int refresh_flags;
 };
 
 static void *preload_thread(void *_data)
@@ -60,6 +61,7 @@ static void *preload_thread(void *_data)
 	do {
 		struct cache_entry *ce = *cep++;
 		struct stat st;
+		unsigned int ce_option = CE_MATCH_RACY_IS_DIRTY | CE_MATCH_IGNORE_FSMONITOR;
 
 		if (ce_stage(ce))
 			continue;
@@ -87,7 +89,9 @@ static void *preload_thread(void *_data)
 		p->t2_nr_lstat++;
 		if (lstat(ce->name, &st))
 			continue;
-		if (ie_match_stat(index, ce, &st, CE_MATCH_RACY_IS_DIRTY|CE_MATCH_IGNORE_FSMONITOR))
+		if (p->refresh_flags & (REFRESH_REALLY | REFRESH_STAT_ONLY))
+			ce_option |= CE_MATCH_IGNORE_VALID;
+		if (ie_match_stat(index, ce, &st, ce_option))
 			continue;
 		ce_mark_uptodate(ce);
 		mark_fsmonitor_valid(index, ce);
@@ -150,6 +154,7 @@ void preload_index(struct index_state *index,
 			copy_pathspec(&p->pathspec, pathspec);
 		p->offset = offset;
 		p->nr = work;
+		p->refresh_flags = refresh_flags;
 		if (pd.progress)
 			p->progress = &pd;
 		offset += work;

read-cache-ll.h

@@ -425,6 +425,8 @@ void *read_blob_data_from_index(struct index_state *, const char *, unsigned lon
 #define CE_MATCH_REFRESH		0x10
 /* don't refresh_fsmonitor state or do stat comparison even if CE_FSMONITOR_VALID is true */
 #define CE_MATCH_IGNORE_FSMONITOR 0X20
+/* update stat info without checking content */
+#define CE_MATCH_STAT_ONLY		0x40
 int is_racy_timestamp(const struct index_state *istate,
 		      const struct cache_entry *ce);
 int has_racy_timestamp(struct index_state *istate);
@@ -452,6 +454,7 @@ int fake_lstat(const struct cache_entry *ce, struct stat *st);
 #define REFRESH_IN_PORCELAIN             (1 << 5) /* user friendly output, not "needs update" */
 #define REFRESH_PROGRESS                 (1 << 6) /* show progress bar if stderr is tty */
 #define REFRESH_IGNORE_SKIP_WORKTREE     (1 << 7) /* ignore skip_worktree entries */
+#define REFRESH_STAT_ONLY                (1 << 8) /* update stat info without checking content */
 int refresh_index(struct index_state *, unsigned int flags, const struct pathspec *pathspec, char *seen, const char *header_msg);
 /*
  * Refresh the index and write it to disk.

read-cache.c

@@ -1350,6 +1350,7 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
 	int ignore_skip_worktree = options & CE_MATCH_IGNORE_SKIP_WORKTREE;
 	int ignore_missing = options & CE_MATCH_IGNORE_MISSING;
 	int ignore_fsmonitor = options & CE_MATCH_IGNORE_FSMONITOR;
+	int stat_only = options & CE_MATCH_STAT_ONLY;
 
 	if (!refresh || ce_uptodate(ce))
 		return ce;
@@ -1420,12 +1421,14 @@ static struct cache_entry *refresh_cache_ent(struct index_state *istate,
 		}
 	}
 
-	if (t2_did_scan)
-		*t2_did_scan = 1;
-	if (ie_modified(istate, ce, &st, options)) {
-		if (err)
-			*err = EINVAL;
-		return NULL;
+	if (!stat_only) {
+		if (t2_did_scan)
+			*t2_did_scan = 1;
+		if (ie_modified(istate, ce, &st, options)) {
+			if (err)
+				*err = EINVAL;
+			return NULL;
+		}
 	}
 
 	updated = make_empty_cache_entry(istate, ce_namelen(ce));
@@ -1490,11 +1493,14 @@ int refresh_index(struct index_state *istate, unsigned int flags,
 	int not_new = (flags & REFRESH_IGNORE_MISSING) != 0;
 	int ignore_submodules = (flags & REFRESH_IGNORE_SUBMODULES) != 0;
 	int ignore_skip_worktree = (flags & REFRESH_IGNORE_SKIP_WORKTREE) != 0;
+	int stat_only = (flags & REFRESH_STAT_ONLY) != 0;
 	int first = 1;
 	int in_porcelain = (flags & REFRESH_IN_PORCELAIN);
 	unsigned int options = (CE_MATCH_REFRESH |
-				(really ? CE_MATCH_IGNORE_VALID : 0) |
-				(not_new ? CE_MATCH_IGNORE_MISSING : 0));
+				((really || stat_only) ? CE_MATCH_IGNORE_VALID : 0) |
+				(not_new ? CE_MATCH_IGNORE_MISSING : 0) |
+				(stat_only ? (CE_MATCH_STAT_ONLY |
+					      CE_MATCH_RACY_IS_DIRTY) : 0));
 	const char *modified_fmt;
 	const char *deleted_fmt;
 	const char *typechange_fmt;
@@ -1520,7 +1526,7 @@ int refresh_index(struct index_state *istate, unsigned int flags,
 	 * cache entries quickly then in the single threaded loop below,
 	 * we only have to do the special cases that are left.
 	 */
-	preload_index(istate, pathspec, 0);
+	preload_index(istate, pathspec, flags & (REFRESH_REALLY | REFRESH_STAT_ONLY));
 	trace2_region_enter("index", "refresh", NULL);
 
 	for (i = 0; i < istate->cache_nr; i++) {

t/meson.build

@@ -291,6 +291,7 @@ integration_tests = [
   't2106-update-index-assume-unchanged.sh',
   't2107-update-index-basic.sh',
   't2108-update-index-refresh-racy.sh',
+  't2109-update-index-refresh-stat-only.sh',
   't2200-add-update.sh',
   't2201-add-update-typechange.sh',
   't2202-add-addremove.sh',

t/t2106-update-index-assume-unchanged.sh

@@ -24,4 +24,15 @@ test_expect_success 'do not switch branches with dirty file' '
 	test_grep overwritten err
 '
 
+test_expect_success '--really-refresh overrides assume-unchanged under preload' '
+	git reset --hard &&
+	test_commit really-refresh really-refresh original &&
+	git update-index --assume-unchanged really-refresh &&
+	printf "modified\n" >really-refresh &&
+	test-tool chmtime -100000 really-refresh &&
+	test_must_fail env GIT_TEST_PRELOAD_INDEX=1 \
+		git update-index --really-refresh >out 2>err &&
+	test_grep "needs update" out
+'
+
 test_done

t/t2109-update-index-refresh-stat-only.sh

@@ -0,0 +1,59 @@
+#!/bin/sh
+
+test_description='git update-index --refresh-stat-only'
+
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_commit initial base-file base
+'
+
+test_expect_success '--refresh-stat-only updates stat info without rehashing' '
+	test_commit refresh-stat refresh-stat original &&
+	git ls-files --stage -- refresh-stat >expect &&
+	git ls-files --debug refresh-stat | grep mtime >before &&
+	printf "modified\n" >refresh-stat &&
+	test-tool chmtime -100000 refresh-stat &&
+	test_must_fail git diff-files --quiet -- refresh-stat &&
+	git update-index --refresh-stat-only &&
+	git ls-files --debug refresh-stat | grep mtime >after &&
+	! test_cmp before after &&
+	git ls-files --stage -- refresh-stat >actual &&
+	test_cmp expect actual &&
+	git diff-files --quiet -- refresh-stat
+'
+
+test_expect_success '--refresh-stat-only ignores assume-unchanged' '
+	test_commit assume-unchanged assume-unchanged old &&
+	git update-index --assume-unchanged assume-unchanged &&
+	printf "new\n" >assume-unchanged &&
+	test-tool chmtime -100000 assume-unchanged &&
+	GIT_TEST_PRELOAD_INDEX=1 git update-index --refresh-stat-only &&
+	git update-index --no-assume-unchanged assume-unchanged &&
+	git diff-files --quiet -- assume-unchanged
+'
+
+test_expect_success '--refresh-stat-only with missing file and --ignore-missing' '
+	test_commit missing-ignore missing-ignore content &&
+	rm missing-ignore &&
+	git update-index --ignore-missing --refresh-stat-only &&
+	git checkout -- missing-ignore
+'
+
+test_expect_success '--refresh-stat-only reports error on missing file without --ignore-missing' '
+	test_commit missing-error missing-error content &&
+	rm missing-error &&
+	test_must_fail git update-index --refresh-stat-only >out 2>err &&
+	test_grep "needs update" out &&
+	git checkout -- missing-error
+'
+
+test_expect_success '--refresh-stat-only with -q is quiet' '
+	test_commit missing-quiet missing-quiet content &&
+	rm missing-quiet &&
+	git update-index -q --ignore-missing --refresh-stat-only >out 2>err &&
+	test_must_be_empty out &&
+	test_must_be_empty err
+'
+
+test_done