ll-merge: make callers responsible for showing warnings

Since some callers may want to send warning messages to somewhere other
than stdout/stderr, stop printing "warning: Cannot merge binary files"
from ll-merge and instead modify the return status of ll_merge() to
indicate when a merge of binary files has occurred.  Message printing
probably does not belong in a "low-level merge" anyway.

This commit continues printing the message as-is, just from the callers
instead of within ll_merge().  Future changes will start handling the
message differently in the merge-ort codepath.

There was one special case here: the callers in rerere.c do NOT check
for and print such a message; since those code paths explicitly skip
over binary files, there is no reason to check for a return status of
LL_MERGE_BINARY_CONFLICT or print the related message.

Note that my methodology included first modifying ll_merge() to return
a struct, so that the compiler would catch all the callers for me and
ensure I had modified all of them.  After modifying all of them, I then
changed the struct to an enum.

Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 22 insertions, 18 deletions

diff --git a/ll-merge.c b/ll-merge.c
index 261657578c..a937cec59a 100644
--- a/ll-merge.c
+++ b/ll-merge.c
@@ -14,7 +14,7 @@
 
 struct ll_merge_driver;
 
-typedef int (*ll_merge_fn)(const struct ll_merge_driver *,
+typedef enum ll_merge_result (*ll_merge_fn)(const struct ll_merge_driver *,
 			   mmbuffer_t *result,
 			   const char *path,
 			   mmfile_t *orig, const char *orig_name,
@@ -49,7 +49,7 @@ void reset_merge_attributes(void)
 /*
  * Built-in low-levels
  */
-static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
+static enum ll_merge_result ll_binary_merge(const struct ll_merge_driver *drv_unused,
 			   mmbuffer_t *result,
 			   const char *path,
 			   mmfile_t *orig, const char *orig_name,
@@ -58,6 +58,7 @@ static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
 			   const struct ll_merge_options *opts,
 			   int marker_size)
 {
+	enum ll_merge_result ret;
 	mmfile_t *stolen;
 	assert(opts);
 
@@ -68,16 +69,19 @@ static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
 	 */
 	if (opts->virtual_ancestor) {
 		stolen = orig;
+		ret = LL_MERGE_OK;
 	} else {
 		switch (opts->variant) {
 		default:
-			warning("Cannot merge binary files: %s (%s vs. %s)",
-				path, name1, name2);
-			/* fallthru */
+			ret = LL_MERGE_BINARY_CONFLICT;
+			stolen = src1;
+			break;
 		case XDL_MERGE_FAVOR_OURS:
+			ret = LL_MERGE_OK;
 			stolen = src1;
 			break;
 		case XDL_MERGE_FAVOR_THEIRS:
+			ret = LL_MERGE_OK;
 			stolen = src2;
 			break;
 		}
@@ -87,16 +91,10 @@ static int ll_binary_merge(const struct ll_merge_driver *drv_unused,
 	result->size = stolen->size;
 	stolen->ptr = NULL;
 
-	/*
-	 * With -Xtheirs or -Xours, we have cleanly merged;
-	 * otherwise we got a conflict.
-	 */
-	return opts->variant == XDL_MERGE_FAVOR_OURS ||
-	       opts->variant == XDL_MERGE_FAVOR_THEIRS ?
-	       0 : 1;
+	return ret;
 }
 
-static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
+static enum ll_merge_result ll_xdl_merge(const struct ll_merge_driver *drv_unused,
 			mmbuffer_t *result,
 			const char *path,
 			mmfile_t *orig, const char *orig_name,
@@ -105,7 +103,9 @@ static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
 			const struct ll_merge_options *opts,
 			int marker_size)
 {
+	enum ll_merge_result ret;
 	xmparam_t xmp;
+	int status;
 	assert(opts);
 
 	if (orig->size > MAX_XDIFF_SIZE ||
@@ -133,10 +133,12 @@ static int ll_xdl_merge(const struct ll_merge_driver *drv_unused,
 	xmp.ancestor = orig_name;
 	xmp.file1 = name1;
 	xmp.file2 = name2;
-	return xdl_merge(orig, src1, src2, &xmp, result);
+	status = xdl_merge(orig, src1, src2, &xmp, result);
+	ret = (status > 0) ? LL_MERGE_CONFLICT : status;
+	return ret;
 }
 
-static int ll_union_merge(const struct ll_merge_driver *drv_unused,
+static enum ll_merge_result ll_union_merge(const struct ll_merge_driver *drv_unused,
 			  mmbuffer_t *result,
 			  const char *path,
 			  mmfile_t *orig, const char *orig_name,
@@ -178,7 +180,7 @@ static void create_temp(mmfile_t *src, char *path, size_t len)
 /*
  * User defined low-level merge driver support.
  */
-static int ll_ext_merge(const struct ll_merge_driver *fn,
+static enum ll_merge_result ll_ext_merge(const struct ll_merge_driver *fn,
 			mmbuffer_t *result,
 			const char *path,
 			mmfile_t *orig, const char *orig_name,
@@ -194,6 +196,7 @@ static int ll_ext_merge(const struct ll_merge_driver *fn,
 	const char *args[] = { NULL, NULL };
 	int status, fd, i;
 	struct stat st;
+	enum ll_merge_result ret;
 	assert(opts);
 
 	sq_quote_buf(&path_sq, path);
@@ -236,7 +239,8 @@ static int ll_ext_merge(const struct ll_merge_driver *fn,
 		unlink_or_warn(temp[i]);
 	strbuf_release(&cmd);
 	strbuf_release(&path_sq);
-	return status;
+	ret = (status > 0) ? LL_MERGE_CONFLICT : status;
+	return ret;
 }
 
 /*
@@ -362,7 +366,7 @@ static void normalize_file(mmfile_t *mm, const char *path, struct index_state *i
 	}
 }
 
-int ll_merge(mmbuffer_t *result_buf,
+enum ll_merge_result ll_merge(mmbuffer_t *result_buf,
 	     const char *path,
 	     mmfile_t *ancestor, const char *ancestor_label,
 	     mmfile_t *ours, const char *our_label,