merge: merge with the default upstream branch without argument

"git merge" without specifying any commit is a no-op by default.

A new option merge.defaultupstream can be set to true to cause such an
invocation of the command to merge the upstream branches configured for
the current branch by using their last observed values stored in their
remote tracking branches.

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

1 files changed, 38 insertions, 1 deletions

diff --git a/builtin/merge.c b/builtin/merge.c
index a2105ef90c..309bdd4dc7 100644
--- a/builtin/merge.c
+++ b/builtin/merge.c
@@ -25,6 +25,7 @@
 #include "help.h"
 #include "merge-recursive.h"
 #include "resolve-undo.h"
+#include "remote.h"
 
 #define DEFAULT_TWOHEAD (1<<0)
 #define DEFAULT_OCTOPUS (1<<1)
@@ -37,7 +38,7 @@ struct strategy {
 };
 
 static const char * const builtin_merge_usage[] = {
-	"git merge [options] <commit>...",
+	"git merge [options] [<commit>...]",
 	"git merge [options] <msg> HEAD <commit>",
 	"git merge --abort",
 	NULL
@@ -59,6 +60,7 @@ static int option_renormalize;
 static int verbosity;
 static int allow_rerere_auto;
 static int abort_current_merge;
+static int default_to_upstream;
 
 static struct strategy all_strategy[] = {
 	{ "recursive",  DEFAULT_TWOHEAD | NO_TRIVIAL },
@@ -537,6 +539,9 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 		if (is_bool && shortlog_len)
 			shortlog_len = DEFAULT_MERGE_LOG_LEN;
 		return 0;
+	} else if (!strcmp(k, "merge.defaulttoupstream")) {
+		default_to_upstream = git_config_bool(k, v);
+		return 0;
 	}
 	return git_diff_ui_config(k, v, cb);
 }
@@ -912,6 +917,35 @@ static int evaluate_result(void)
 	return cnt;
 }
 
+/*
+ * Pretend as if the user told us to merge with the tracking
+ * branch we have for the upstream of the current branch
+ */
+static int setup_with_upstream(const char ***argv)
+{
+	struct branch *branch = branch_get(NULL);
+	int i;
+	const char **args;
+
+	if (!branch)
+		die("No current branch.");
+	if (!branch->remote)
+		die("No remote for the current branch.");
+	if (!branch->merge_nr)
+		die("No default upstream defined for the current branch.");
+
+	args = xcalloc(branch->merge_nr + 1, sizeof(char *));
+	for (i = 0; i < branch->merge_nr; i++) {
+		if (!branch->merge[i]->dst)
+			die("No remote tracking branch for %s from %s",
+			    branch->merge[i]->src, branch->remote_name);
+		args[i] = branch->merge[i]->dst;
+	}
+	args[i] = NULL;
+	*argv = args;
+	return i;
+}
+
 int cmd_merge(int argc, const char **argv, const char *prefix)
 {
 	unsigned char result_tree[20];
@@ -984,6 +1018,9 @@ int cmd_merge(int argc, const char **argv, const char *prefix)
 	if (!allow_fast_forward && fast_forward_only)
 		die("You cannot combine --no-ff with --ff-only.");
 
+	if (!argc && !abort_current_merge && default_to_upstream)
+		argc = setup_with_upstream(&argv);
+
 	if (!argc)
 		usage_with_options(builtin_merge_usage,
 			builtin_merge_options);