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>

Makefile

@@ -765,7 +765,7 @@ LIB_OBJS += log-tree.o
 LIB_OBJS += mailmap.o
 LIB_OBJS += match-trees.o
 LIB_OBJS += merge.o
-LIB_OBJS += merge-file.o
+LIB_OBJS += merge-blobs.o
 LIB_OBJS += merge-recursive.o
 LIB_OBJS += mergesort.o
 LIB_OBJS += name-hash.o

builtin/merge-index.c

@@ -42,7 +42,7 @@ static int merge_entry(int pos, const char *path)
 	return found;
 }
 
-static void merge_file(const char *path)
+static void merge_one_path(const char *path)
 {
 	int pos = cache_name_pos(path, strlen(path));
 
@@ -102,7 +102,7 @@ int cmd_merge_index(int argc, const char **argv, const char *prefix)
 			}
 			die("git merge-index: unknown option %s", arg);
 		}
-		merge_file(arg);
+		merge_one_path(arg);
 	}
 	if (err && !quiet)
 		die("merge program failed");

builtin/merge-tree.c

@@ -3,7 +3,7 @@
 #include "xdiff-interface.h"
 #include "blob.h"
 #include "exec_cmd.h"
-#include "merge-file.h"
+#include "merge-blobs.h"
 
 static const char merge_tree_usage[] = "git merge-tree <base-tree> <branch1> <branch2>";
 static int resolve_directories = 1;
@@ -76,7 +76,7 @@ static void *result(struct merge_list *entry, unsigned long *size)
 	their = NULL;
 	if (entry)
 		their = entry->blob;
-	return merge_file(path, base, our, their, size);
+	return merge_blobs(path, base, our, their, size);
 }
 
 static void *origin(struct merge_list *entry, unsigned long *size)

merge-file.c → merge-blobs.c

@@ -3,7 +3,7 @@
 #include "xdiff-interface.h"
 #include "ll-merge.h"
 #include "blob.h"
-#include "merge-file.h"
+#include "merge-blobs.h"
 
 static int fill_mmfile_blob(mmfile_t *f, struct blob *obj)
 {
@@ -80,7 +80,7 @@ static int generate_common_file(mmfile_t *res, mmfile_t *f1, mmfile_t *f2)
 	return xdi_diff(f1, f2, &xpp, &xecfg, &ecb);
 }
 
-void *merge_file(const char *path, struct blob *base, struct blob *our, struct blob *their, unsigned long *size)
+void *merge_blobs(const char *path, struct blob *base, struct blob *our, struct blob *their, unsigned long *size)
 {
 	void *res = NULL;
 	mmfile_t f1, f2, common;

merge-blobs.h

@@ -0,0 +1,8 @@
+#ifndef MERGE_BLOBS_H
+#define MERGE_BLOBS_H
+
+#include "blob.h"
+
+extern void *merge_blobs(const char *, struct blob *, struct blob *, struct blob *, unsigned long *);
+
+#endif /* MERGE_BLOBS_H */

merge-recursive.c

@@ -976,7 +976,7 @@ merge_file_special_markers(struct merge_options *o,
 	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 @@ static void conflict_rename_rename_1to2(struct merge_options *o,
 		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 @@ static int process_renames(struct merge_options *o,
 				       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);