Convert "struct cache_entry *" to "const ..." wherever possiblend/const-struct-cache-entry

I attempted to make index_state->cache[] a "const struct cache_entry **"
to find out how existing entries in index are modified and where. The
question I have is what do we do if we really need to keep track of on-disk
changes in the index. The result is

 - diff-lib.c: setting CE_UPTODATE

 - name-hash.c: setting CE_HASHED

 - preload-index.c, read-cache.c, unpack-trees.c and
   builtin/update-index: obvious

 - entry.c: write_entry() may refresh the checked out entry via
   fill_stat_cache_info(). This causes "non-const struct cache_entry
   *" in builtin/apply.c, builtin/checkout-index.c and
   builtin/checkout.c

 - builtin/ls-files.c: --with-tree changes stagemask and may set
   CE_UPDATE

Of these, write_entry() and its call sites are probably most
interesting because it modifies on-disk info. But this is stat info
and can be retrieved via refresh, at least for porcelain
commands. Other just uses ce_flags for local purposes.

So, keeping track of "dirty" entries is just a matter of setting a
flag in index modification functions exposed by read-cache.c. Except
unpack-trees, the rest of the code base does not do anything funny
behind read-cache's back.

The actual patch is less valueable than the summary above. But if
anyone wants to re-identify the above sites. Applying this patch, then
this:

    diff --git a/cache.h b/cache.h
    index 430d021..1692891 100644
    --- a/cache.h
    +++ b/cache.h
    @@ -267,7 +267,7 @@ static inline unsigned int canon_mode(unsigned int mode)
     #define cache_entry_size(len) (offsetof(struct cache_entry,name) + (len) + 1)

     struct index_state {
    -	struct cache_entry **cache;
    +	const struct cache_entry **cache;
     	unsigned int version;
     	unsigned int cache_nr, cache_alloc, cache_changed;
     	struct string_list *resolve_undo;

will help quickly identify them without bogus warnings.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 6 insertions, 6 deletions

diff --git a/rerere.c b/rerere.c
index 98e3e294d0..6fde8f94c2 100644
--- a/rerere.c
+++ b/rerere.c
@@ -299,7 +299,7 @@ static int handle_cache(const char *path, unsigned char *sha1, const char *outpu
 {
 	mmfile_t mmfile[3] = {{NULL}};
 	mmbuffer_t result = {NULL, 0};
-	struct cache_entry *ce;
+	const struct cache_entry *ce;
 	int pos, len, i, hunk_no;
 	struct rerere_io_mem io;
 	int marker_size = ll_merge_marker_size(path);
@@ -359,7 +359,7 @@ static int handle_cache(const char *path, unsigned char *sha1, const char *outpu
 
 static int check_one_conflict(int i, int *type)
 {
-	struct cache_entry *e = active_cache[i];
+	const struct cache_entry *e = active_cache[i];
 
 	if (!ce_stage(e)) {
 		*type = RESOLVED;
@@ -374,8 +374,8 @@ static int check_one_conflict(int i, int *type)
 
 	/* Only handle regular files with both stages #2 and #3 */
 	if (i + 1 < active_nr) {
-		struct cache_entry *e2 = active_cache[i];
-		struct cache_entry *e3 = active_cache[i + 1];
+		const struct cache_entry *e2 = active_cache[i];
+		const struct cache_entry *e3 = active_cache[i + 1];
 		if (ce_stage(e2) == 2 &&
 		    ce_stage(e3) == 3 &&
 		    ce_same_name(e, e3) &&
@@ -398,7 +398,7 @@ static int find_conflict(struct string_list *conflict)
 
 	for (i = 0; i < active_nr;) {
 		int conflict_type;
-		struct cache_entry *e = active_cache[i];
+		const struct cache_entry *e = active_cache[i];
 		i = check_one_conflict(i, &conflict_type);
 		if (conflict_type == THREE_STAGED)
 			string_list_insert(conflict, (const char *)e->name);
@@ -414,7 +414,7 @@ int rerere_remaining(struct string_list *merge_rr)
 
 	for (i = 0; i < active_nr;) {
 		int conflict_type;
-		struct cache_entry *e = active_cache[i];
+		const struct cache_entry *e = active_cache[i];
 		i = check_one_conflict(i, &conflict_type);
 		if (conflict_type == PUNTED)
 			string_list_insert(merge_rr, (const char *)e->name);