[PATCH 2/3] move index_has_changes() from builtin/am.c to merge.c for reuse

[Elijah Newren <newren@gmail.com>]

index_has_changes() is a function we want to reuse outside of just am,
making it also available for merge-recursive and merge-ort.

Signed-off-by: Elijah Newren <newren@gmail.com>
---
 builtin/am.c | 37 -------------------------------------
 cache.h      |  9 +++++++++
 merge.c      | 33 +++++++++++++++++++++++++++++++++
 3 files changed, 42 insertions(+), 37 deletions(-)

diff --git a/builtin/am.c b/builtin/am.c
index 3d98e52085..a02d5186cb 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1142,43 +1142,6 @@ static void refresh_and_write_cache(void)
 		die(_("unable to write index file"));
 }
 
-/**
- * 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.
- */
-static int index_has_changes(struct strbuf *sb)
-{
-	struct object_id head;
-	int i;
-
-	if (!get_oid_tree("HEAD", &head)) {
-		struct diff_options opt;
-
-		diff_setup(&opt);
-		opt.flags.exit_with_status = 1;
-		if (!sb)
-			opt.flags.quick = 1;
-		do_diff_cache(&head, &opt);
-		diffcore_std(&opt);
-		for (i = 0; sb && i < diff_queued_diff.nr; i++) {
-			if (i)
-				strbuf_addch(sb, ' ');
-			strbuf_addstr(sb, diff_queued_diff.queue[i]->two->path);
-		}
-		diff_flush(&opt);
-		return opt.flags.has_changes != 0;
-	} else {
-		for (i = 0; sb && i < active_nr; i++) {
-			if (i)
-				strbuf_addch(sb, ' ');
-			strbuf_addstr(sb, active_cache[i]->name);
-		}
-		return !!active_nr;
-	}
-}
-
 /**
  * Dies with a user-friendly message on how to proceed after resolving the
  * problem. This message can be overridden with state->resolvemsg.
diff --git a/cache.h b/cache.h
index a2ec8c0b55..d8b975a571 100644
--- a/cache.h
+++ b/cache.h
@@ -644,6 +644,15 @@ extern int write_locked_index(struct index_state *, struct lock_file *lock, unsi
 extern int discard_index(struct index_state *);
 extern void move_index_extensions(struct index_state *dst, struct index_state *src);
 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.
+ */
+extern int index_has_changes(struct strbuf *sb);
+
 extern int verify_path(const char *path);
 extern int strcmp_offset(const char *s1, const char *s2, size_t *first_change);
 extern int index_dir_exists(struct index_state *istate, const char *name, int namelen);
diff --git a/merge.c b/merge.c
index e5d796c9f2..195b578700 100644
--- a/merge.c
+++ b/merge.c
@@ -1,4 +1,6 @@
 #include "cache.h"
+#include "diff.h"
+#include "diffcore.h"
 #include "lockfile.h"
 #include "commit.h"
 #include "run-command.h"
@@ -15,6 +17,37 @@ static const char *merge_argument(struct commit *commit)
 		return EMPTY_TREE_SHA1_HEX;
 }
 
+int index_has_changes(struct strbuf *sb)
+{
+	struct object_id head;
+	int i;
+
+	if (!get_oid_tree("HEAD", &head)) {
+		struct diff_options opt;
+
+		diff_setup(&opt);
+		opt.flags.exit_with_status = 1;
+		if (!sb)
+			opt.flags.quick = 1;
+		do_diff_cache(&head, &opt);
+		diffcore_std(&opt);
+		for (i = 0; sb && i < diff_queued_diff.nr; i++) {
+			if (i)
+				strbuf_addch(sb, ' ');
+			strbuf_addstr(sb, diff_queued_diff.queue[i]->two->path);
+		}
+		diff_flush(&opt);
+		return opt.flags.has_changes != 0;
+	} else {
+		for (i = 0; sb && i < active_nr; i++) {
+			if (i)
+				strbuf_addch(sb, ' ');
+			strbuf_addstr(sb, active_cache[i]->name);
+		}
+		return !!active_nr;
+	}
+}
+
 int try_merge_command(const char *strategy, size_t xopts_nr,
 		      const char **xopts, struct commit_list *common,
 		      const char *head_arg, struct commit_list *remotes)
-- 
2.15.1.436.g63a861020b