move index_has_changes() from builtin/am.c to merge.c for reuse

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>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 33 insertions, 0 deletions

diff --git a/merge.c b/merge.c
index 1d441ad942..b0714bc85e 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);
+		DIFF_OPT_SET(&opt, EXIT_WITH_STATUS);
+		if (!sb)
+			DIFF_OPT_SET(&opt, QUICK);
+		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 DIFF_OPT_TST(&opt, 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)