Build-in merge-recursive

This makes write_tree_from_memory(), which writes the active cache as
a tree and returns the struct tree for it, available to other code. It
also makes available merge_trees(), which does the internal merge of
two trees with a known base, and merge_recursive(), which does the
recursive internal merge of two commits with a list of common
ancestors.

The first two of these will be used by checkout -m, and the third is
presumably useful in general, although the implementation of checkout
-m which entirely matches the behavior of the shell version does not
use it (since it ignores the difference of ancestry between the old
branch and the new branch).

Signed-off-by: Daniel Barkalow <barkalow@iabervon.org>

Makefile

@@ -256,7 +256,6 @@ PROGRAMS = \
 	git-upload-pack$X \
 	git-pack-redundant$X git-var$X \
 	git-merge-tree$X git-imap-send$X \
-	git-merge-recursive$X \
 	$(EXTRA_PROGRAMS)
 
 # Empty...
@@ -360,6 +359,7 @@ BUILTIN_OBJS = \
 	builtin-merge-base.o \
 	builtin-merge-file.o \
 	builtin-merge-ours.o \
+	builtin-merge-recursive.o \
 	builtin-mv.o \
 	builtin-name-rev.o \
 	builtin-pack-objects.o \

builtin-merge-recursive.c

@@ -7,6 +7,7 @@
 #include "cache-tree.h"
 #include "commit.h"
 #include "blob.h"
+#include "builtin.h"
 #include "tree-walk.h"
 #include "diff.h"
 #include "diffcore.h"
@@ -17,6 +18,7 @@
 #include "xdiff-interface.h"
 #include "interpolate.h"
 #include "attr.h"
+#include "merge-recursive.h"
 
 static int subtree_merge;
 
@@ -232,7 +234,7 @@ static int unmerged_index(void)
 	return 0;
 }
 
-static struct tree *git_write_tree(void)
+struct tree *write_tree_from_memory(void)
 {
 	struct tree *result = NULL;
 
@@ -1495,7 +1497,7 @@ static int process_entry(const char *path, struct stage_data *entry,
 	return clean_merge;
 }
 
-static int merge_trees(struct tree *head,
+int merge_trees(struct tree *head,
 		struct tree *merge,
 		struct tree *common,
 		const char *branch1,
@@ -1552,7 +1554,7 @@ static int merge_trees(struct tree *head,
 		clean = 1;
 
 	if (index_only)
-		*result = git_write_tree();
+		*result = write_tree_from_memory();
 
 	return clean;
 }
@@ -1572,7 +1574,7 @@ static struct commit_list *reverse_commit_list(struct commit_list *list)
  * Merge the commits h1 and h2, return the resulting virtual
  * commit object and a flag indicating the cleanness of the merge.
  */
-static int merge(struct commit *h1,
+int merge_recursive(struct commit *h1,
 		    struct commit *h2,
 		    const char *branch1,
 		    const char *branch2,
@@ -1622,7 +1624,7 @@ static int merge(struct commit *h1,
 		 * "conflicts" were already resolved.
 		 */
 		discard_cache();
-		merge(merged_common_ancestors, iter->item,
+		merge_recursive(merged_common_ancestors, iter->item,
 				"Temporary merge branch 1",
 				"Temporary merge branch 2",
 				NULL,
@@ -1695,7 +1697,7 @@ static int merge_config(const char *var, const char *value)
 	return git_default_config(var, value);
 }
 
-int main(int argc, char *argv[])
+int cmd_merge_recursive(int argc, const char **argv, const char *prefix)
 {
 	static const char *bases[20];
 	static unsigned bases_count = 0;
@@ -1749,7 +1751,7 @@ int main(int argc, char *argv[])
 		struct commit *ancestor = get_ref(bases[i]);
 		ca = commit_list_insert(ancestor, &ca);
 	}
-	clean = merge(h1, h2, branch1, branch2, ca, &result);
+	clean = merge_recursive(h1, h2, branch1, branch2, ca, &result);
 
 	if (active_cache_changed &&
 	    (write_cache(index_fd, active_cache, active_nr) ||

builtin.h

@@ -57,6 +57,7 @@ extern int cmd_mailsplit(int argc, const char **argv, const char *prefix);
 extern int cmd_merge_base(int argc, const char **argv, const char *prefix);
 extern int cmd_merge_ours(int argc, const char **argv, const char *prefix);
 extern int cmd_merge_file(int argc, const char **argv, const char *prefix);
+extern int cmd_merge_recursive(int argc, const char **argv, const char *prefix);
 extern int cmd_mv(int argc, const char **argv, const char *prefix);
 extern int cmd_name_rev(int argc, const char **argv, const char *prefix);
 extern int cmd_pack_objects(int argc, const char **argv, const char *prefix);

git.c

@@ -330,6 +330,7 @@ static void handle_internal_command(int argc, const char **argv)
 		{ "merge-base", cmd_merge_base, RUN_SETUP },
 		{ "merge-file", cmd_merge_file },
 		{ "merge-ours", cmd_merge_ours, RUN_SETUP },
+		{ "merge-recursive", cmd_merge_recursive, RUN_SETUP | NEED_WORK_TREE },
 		{ "mv", cmd_mv, RUN_SETUP | NEED_WORK_TREE },
 		{ "name-rev", cmd_name_rev, RUN_SETUP },
 		{ "pack-objects", cmd_pack_objects, RUN_SETUP },

merge-recursive.h

@@ -0,0 +1,20 @@
+#ifndef MERGE_RECURSIVE_H
+#define MERGE_RECURSIVE_H
+
+int merge_recursive(struct commit *h1,
+		    struct commit *h2,
+		    const char *branch1,
+		    const char *branch2,
+		    struct commit_list *ancestors,
+		    struct commit **result);
+
+int merge_trees(struct tree *head,
+		struct tree *merge,
+		struct tree *common,
+		const char *branch1,
+		const char *branch2,
+		struct tree **result);
+
+struct tree *write_tree_from_memory(void);
+
+#endif