index_has_changes(): avoid assuming operating on the_index

Modify index_has_changes() to take a struct istate* instead of just
operating on the_index.  This is only a partial conversion, though,
because we call do_diff_cache() which implicitly assumes work is to be
done on the_index.  Ongoing work is being done elsewhere to do the
remainder of the conversion, and thus is not duplicated here.  Instead,
a simple check is put in place until that work is complete.

Signed-off-by: Elijah Newren <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: newren

builtin/am.c

@@ -1763,7 +1763,7 @@ static void am_run(struct am_state *state, int resume)
 
 	refresh_and_write_cache();
 
-	if (index_has_changes(&sb)) {
+	if (index_has_changes(&the_index, &sb)) {
 		write_state_bool(state, "dirtyindex", 1);
 		die(_("Dirty index: cannot apply patches (dirty: %s)"), sb.buf);
 	}
@@ -1820,7 +1820,7 @@ static void am_run(struct am_state *state, int resume)
 			 * Applying the patch to an earlier tree and merging
 			 * the result may have produced the same tree as ours.
 			 */
-			if (!apply_status && !index_has_changes(NULL)) {
+			if (!apply_status && !index_has_changes(&the_index, NULL)) {
 				say(state, stdout, _("No changes -- Patch already applied."));
 				goto next;
 			}
@@ -1878,7 +1878,7 @@ static void am_resolve(struct am_state *state)
 
 	say(state, stdout, _("Applying: %.*s"), linelen(state->msg), state->msg);
 
-	if (!index_has_changes(NULL)) {
+	if (!index_has_changes(&the_index, NULL)) {
 		printf_ln(_("No changes - did you forget to use 'git add'?\n"
 			"If there is nothing left to stage, chances are that something else\n"
 			"already introduced the same changes; you might want to skip this patch."));

cache.h

@@ -627,12 +627,13 @@ extern void move_index_extensions(struct index_state *dst, struct index_state *s
 extern int unmerged_index(const struct index_state *);
 
 /**
- * Returns 1 if the index differs from HEAD, 0 otherwise. When on an unborn
- * branch, returns 1 if there are entries in the index, 0 otherwise. If an
- * strbuf is provided, the space-separated list of files that differ will be
- * appended to it.
+ * Returns 1 if istate differs from HEAD, 0 otherwise.  When on an unborn
+ * branch, returns 1 if there are entries in istate, 0 otherwise.  If an
+ * strbuf is provided, the space-separated list of files that differ will
+ * be appended to it.
  */
-extern int index_has_changes(struct strbuf *sb);
+extern int index_has_changes(const struct index_state *istate,
+			     struct strbuf *sb);
 
 extern int verify_path(const char *path, unsigned mode);
 extern int strcmp_offset(const char *s1, const char *s2, size_t *first_change);

merge-recursive.c

@@ -1983,7 +1983,7 @@ int merge_trees(struct merge_options *o,
 	if (oid_eq(&common->object.oid, &merge->object.oid)) {
 		struct strbuf sb = STRBUF_INIT;
 
-		if (!o->call_depth && index_has_changes(&sb)) {
+		if (!o->call_depth && index_has_changes(&the_index, &sb)) {
 			err(o, _("Dirty index: cannot merge (dirty: %s)"),
 			    sb.buf);
 			return 0;

read-cache.c

@@ -1986,11 +1986,14 @@ int unmerged_index(const struct index_state *istate)
 	return 0;
 }
 
-int index_has_changes(struct strbuf *sb)
+int index_has_changes(const struct index_state *istate, struct strbuf *sb)
 {
 	struct object_id head;
 	int i;
 
+	if (istate != &the_index) {
+		BUG("index_has_changes cannot yet accept istate != &the_index; do_diff_cache needs updating first.");
+	}
 	if (!get_oid_tree("HEAD", &head)) {
 		struct diff_options opt;
 
@@ -2008,12 +2011,12 @@ int index_has_changes(struct strbuf *sb)
 		diff_flush(&opt);
 		return opt.flags.has_changes != 0;
 	} else {
-		for (i = 0; sb && i < the_index.cache_nr; i++) {
+		for (i = 0; sb && i < istate->cache_nr; i++) {
 			if (i)
 				strbuf_addch(sb, ' ');
-			strbuf_addstr(sb, the_index.cache[i]->name);
+			strbuf_addstr(sb, istate->cache[i]->name);
 		}
-		return !!the_index.cache_nr;
+		return !!istate->cache_nr;
 	}
 }