Move create_branch into a library file

You can also create branches, in exactly the same way, with checkout -b.

This introduces branch.{c,h} library files for doing porcelain-level
operations on branches (such as creating them with their appropriate
default configuration).

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

1 files changed, 140 insertions, 0 deletions

diff --git a/branch.c b/branch.c
new file mode 100644
index 0000000000..45ab820c4a
--- /dev/null
+++ b/branch.c
@@ -0,0 +1,140 @@
+#include "cache.h"
+#include "branch.h"
+#include "refs.h"
+#include "remote.h"
+#include "commit.h"
+
+struct tracking {
+	struct refspec spec;
+	char *src;
+	const char *remote;
+	int matches;
+};
+
+static int find_tracked_branch(struct remote *remote, void *priv)
+{
+	struct tracking *tracking = priv;
+
+	if (!remote_find_tracking(remote, &tracking->spec)) {
+		if (++tracking->matches == 1) {
+			tracking->src = tracking->spec.src;
+			tracking->remote = remote->name;
+		} else {
+			free(tracking->spec.src);
+			if (tracking->src) {
+				free(tracking->src);
+				tracking->src = NULL;
+			}
+		}
+		tracking->spec.src = NULL;
+	}
+
+	return 0;
+}
+
+/*
+ * This is called when new_ref is branched off of orig_ref, and tries
+ * to infer the settings for branch.<new_ref>.{remote,merge} from the
+ * config.
+ */
+static int setup_tracking(const char *new_ref, const char *orig_ref)
+{
+	char key[1024];
+	struct tracking tracking;
+
+	if (strlen(new_ref) > 1024 - 7 - 7 - 1)
+		return error("Tracking not set up: name too long: %s",
+				new_ref);
+
+	memset(&tracking, 0, sizeof(tracking));
+	tracking.spec.dst = (char *)orig_ref;
+	if (for_each_remote(find_tracked_branch, &tracking) ||
+			!tracking.matches)
+		return 1;
+
+	if (tracking.matches > 1)
+		return error("Not tracking: ambiguous information for ref %s",
+				orig_ref);
+
+	if (tracking.matches == 1) {
+		sprintf(key, "branch.%s.remote", new_ref);
+		git_config_set(key, tracking.remote ?  tracking.remote : ".");
+		sprintf(key, "branch.%s.merge", new_ref);
+		git_config_set(key, tracking.src);
+		free(tracking.src);
+		printf("Branch %s set up to track remote branch %s.\n",
+			       new_ref, orig_ref);
+	}
+
+	return 0;
+}
+
+void create_branch(const char *head,
+		   const char *name, const char *start_name,
+		   int force, int reflog, int track)
+{
+	struct ref_lock *lock;
+	struct commit *commit;
+	unsigned char sha1[20];
+	char *real_ref, ref[PATH_MAX], msg[PATH_MAX + 20];
+	int forcing = 0;
+
+	snprintf(ref, sizeof ref, "refs/heads/%s", name);
+	if (check_ref_format(ref))
+		die("'%s' is not a valid branch name.", name);
+
+	if (resolve_ref(ref, sha1, 1, NULL)) {
+		if (!force)
+			die("A branch named '%s' already exists.", name);
+		else if (!is_bare_repository() && !strcmp(head, name))
+			die("Cannot force update the current branch.");
+		forcing = 1;
+	}
+
+	real_ref = NULL;
+	if (get_sha1(start_name, sha1))
+		die("Not a valid object name: '%s'.", start_name);
+
+	switch (dwim_ref(start_name, strlen(start_name), sha1, &real_ref)) {
+	case 0:
+		/* Not branching from any existing branch */
+		real_ref = NULL;
+		break;
+	case 1:
+		/* Unique completion -- good */
+		break;
+	default:
+		die("Ambiguous object name: '%s'.", start_name);
+		break;
+	}
+
+	if ((commit = lookup_commit_reference(sha1)) == NULL)
+		die("Not a valid branch point: '%s'.", start_name);
+	hashcpy(sha1, commit->object.sha1);
+
+	lock = lock_any_ref_for_update(ref, NULL, 0);
+	if (!lock)
+		die("Failed to lock ref for update: %s.", strerror(errno));
+
+	if (reflog)
+		log_all_ref_updates = 1;
+
+	if (forcing)
+		snprintf(msg, sizeof msg, "branch: Reset from %s",
+			 start_name);
+	else
+		snprintf(msg, sizeof msg, "branch: Created from %s",
+			 start_name);
+
+	/* When branching off a remote branch, set up so that git-pull
+	   automatically merges from there.  So far, this is only done for
+	   remotes registered via .git/config.  */
+	if (real_ref && track)
+		setup_tracking(name, real_ref);
+
+	if (write_ref_sha1(lock, sha1, msg) < 0)
+		die("Failed to write ref: %s.", strerror(errno));
+
+	if (real_ref)
+		free(real_ref);
+}