[PATCH v8 2/4] read-cache: pass 'repo' to 'ce_mode_from_stat()'

The ce_mode_from_stat() function is a performance-critical static
inline helper in 'read-cache.h'. As we migrate configuration
variables into the repository struct, this helper needs access
to the repository context.

Update the signature of ce_mode_from_stat() to take a 'struct
repository *' parameter, and update all callers to pass the
appropriate repository instance.

To prepare for the overhead of replacing cheap global variable
accesses with getter functions, the boolean expressions are
reordered to evaluate 'S_ISREG(mode)' first.

While at it, add a comment for ce_mode_from_stat().

Mentored-by: Christian Couder <[email protected]>
Mentored-by: Ayush Chandekar <[email protected]>
Mentored-by: Olamide Caleb Bello <[email protected]>
Signed-off-by: Tian Yuchen <[email protected]>
---
 apply.c                |  2 +-
 builtin/update-index.c |  2 +-
 diff-lib.c             | 10 +++++-----
 read-cache.c           |  2 +-
 read-cache.h           | 15 ++++++++++++---
 5 files changed, 20 insertions(+), 11 deletions(-)

diff --git a/apply.c b/apply.c
index 249248d4f2..26286eb57b 100644
--- a/apply.c
+++ b/apply.c
@@ -3894,7 +3894,7 @@ static int check_preimage(struct apply_state *state,
 			BUG("ce_mode == 0 for path '%s'", old_name);
 
 		if (trust_executable_bit || !S_ISREG(st->st_mode))
-			st_mode = ce_mode_from_stat(*ce, st->st_mode);
+			st_mode = ce_mode_from_stat(state->repo, *ce, st->st_mode);
 		else if (*ce)
 			st_mode = (*ce)->ce_mode;
 		else
diff --git a/builtin/update-index.c b/builtin/update-index.c
index 8a5907767b..7917bd286f 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -293,7 +293,7 @@ static int add_one_path(const struct cache_entry *old, const char *path, int len
 	ce->ce_flags = create_ce_flags(0);
 	ce->ce_namelen = len;
 	fill_stat_cache_info(the_repository->index, ce, st);
-	ce->ce_mode = ce_mode_from_stat(old, st->st_mode);
+	ce->ce_mode = ce_mode_from_stat(the_repository, old, st->st_mode);
 
 	if (index_path(the_repository->index, &ce->oid, path, st,
 		       info_only ? 0 : INDEX_WRITE_OBJECT)) {
diff --git a/diff-lib.c b/diff-lib.c
index ae91027a02..46cae637ec 100644
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -160,7 +160,7 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 
 			changed = check_removed(ce, &st);
 			if (!changed)
-				wt_mode = ce_mode_from_stat(ce, st.st_mode);
+				wt_mode = ce_mode_from_stat(revs->repo, ce, st.st_mode);
 			else {
 				if (changed < 0) {
 					perror(ce->name);
@@ -193,7 +193,7 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 					num_compare_stages++;
 					oidcpy(&dpath->parent[stage - 2].oid,
 					       &nce->oid);
-					dpath->parent[stage-2].mode = ce_mode_from_stat(nce, mode);
+					dpath->parent[stage-2].mode = ce_mode_from_stat(revs->repo, nce, mode);
 					dpath->parent[stage-2].status =
 						DIFF_STATUS_MODIFIED;
 				}
@@ -262,7 +262,7 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 				continue;
 			} else if (revs->diffopt.ita_invisible_in_index &&
 				   ce_intent_to_add(ce)) {
-				newmode = ce_mode_from_stat(ce, st.st_mode);
+				newmode = ce_mode_from_stat(revs->repo, ce, st.st_mode);
 				diff_addremove(&revs->diffopt, '+', newmode,
 					       null_oid(the_hash_algo), 0, ce->name, 0);
 				continue;
@@ -270,7 +270,7 @@ void run_diff_files(struct rev_info *revs, unsigned int option)
 
 			changed = match_stat_with_submodule(&revs->diffopt, ce, &st,
 							    ce_option, &dirty_submodule);
-			newmode = ce_mode_from_stat(ce, st.st_mode);
+			newmode = ce_mode_from_stat(revs->repo, ce, st.st_mode);
 		}
 
 		if (!changed && !dirty_submodule) {
@@ -338,7 +338,7 @@ static int get_stat_data(const struct cache_entry *ce,
 		changed = match_stat_with_submodule(diffopt, ce, &st,
 						    0, dirty_submodule);
 		if (changed) {
-			mode = ce_mode_from_stat(ce, st.st_mode);
+			mode = ce_mode_from_stat(diffopt->repo, ce, st.st_mode);
 			oid = null_oid(the_hash_algo);
 		}
 	}
diff --git a/read-cache.c b/read-cache.c
index c44e4d128f..b37bf688ec 100644
--- a/read-cache.c
+++ b/read-cache.c
@@ -749,7 +749,7 @@ int add_to_index(struct index_state *istate, const char *path, struct stat *st,
 		int pos = index_name_pos_also_unmerged(istate, path, namelen);
 
 		ent = (0 <= pos) ? istate->cache[pos] : NULL;
-		ce->ce_mode = ce_mode_from_stat(ent, st_mode);
+		ce->ce_mode = ce_mode_from_stat(istate->repo, ent, st_mode);
 	}
 
 	/* When core.ignorecase=true, determine if a directory of the same name but differing
diff --git a/read-cache.h b/read-cache.h
index 043da1f1aa..af8c657ecb 100644
--- a/read-cache.h
+++ b/read-cache.h
@@ -4,15 +4,24 @@
 #include "read-cache-ll.h"
 #include "object.h"
 #include "pathspec.h"
+#include "environment.h"
 
-static inline unsigned int ce_mode_from_stat(const struct cache_entry *ce,
+/*
+ * Determine the appropriate index mode for a file based on its stat()
+ * information and the existing cache entry (if any).
+ *
+ * This function handles degradation for filesystems that lack
+ * symlink support or reliable executable bits.
+ */
+static inline unsigned int ce_mode_from_stat(struct repository *repo UNUSED,
+					     const struct cache_entry *ce,
 					     unsigned int mode)
 {
 	extern int trust_executable_bit, has_symlinks;
-	if (!has_symlinks && S_ISREG(mode) &&
+	if (S_ISREG(mode) && !has_symlinks &&
 	    ce && S_ISLNK(ce->ce_mode))
 		return ce->ce_mode;
-	if (!trust_executable_bit && S_ISREG(mode)) {
+	if (S_ISREG(mode) && !trust_executable_bit) {
 		if (ce && S_ISREG(ce->ce_mode))
 			return ce->ce_mode;
 		return create_ce_mode(0666);
-- 
2.43.0