Which merge_file() function do you mean?

There are two different static functions and one global function,
all of them called "merge_file()", with different signatures and
purposes.  Rename them all to reduce confusion in "git grep" output:

 * Rename the static one in merge-index to "merge_one_path(const char
   *path)" as that function is about asking an external command to
   resolve conflicts in one path.

 * Rename the global one in merge-file.c that is only used by
   merge-tree to "merge_blobs()", as the function takes three blobs and
   returns the merged result only in-core, without doing anything to
   the filesystem.

 * Rename the one in merge-recursive to "merge_one_file()", just to be
   fair.

Also rename merge-file.[ch] to merge-blobs.[ch].

Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/merge-recursive.c b/merge-recursive.c
index d882060..33ba5dc 100644
--- a/merge-recursive.c
+++ b/merge-recursive.c
@@ -976,7 +976,7 @@
 	return mfi;
 }
 
-static struct merge_file_info merge_file(struct merge_options *o,
+static struct merge_file_info merge_file_one(struct merge_options *o,
 					 const char *path,
 					 const unsigned char *o_sha, int o_mode,
 					 const unsigned char *a_sha, int a_mode,
@@ -1166,7 +1166,7 @@
 		struct merge_file_info mfi;
 		struct diff_filespec other;
 		struct diff_filespec *add;
-		mfi = merge_file(o, one->path,
+		mfi = merge_file_one(o, one->path,
 				 one->sha1, one->mode,
 				 a->sha1, a->mode,
 				 b->sha1, b->mode,
@@ -1450,7 +1450,7 @@
 				       ren1_dst, branch2);
 				if (o->call_depth) {
 					struct merge_file_info mfi;
-					mfi = merge_file(o, ren1_dst, null_sha1, 0,
+					mfi = merge_file_one(o, ren1_dst, null_sha1, 0,
 							 ren1->pair->two->sha1, ren1->pair->two->mode,
 							 dst_other.sha1, dst_other.mode,
 							 branch1, branch2);