git: Add `create_pull_request_branch()`

This takes in the PR, the index of that PR, and the repo the PR is for,
and will create a branch for that PR in the given repo.

Currently it only supports working with remote branches, but eventually
it'll support patch files too.

2 files changed, 88 insertions, 0 deletions

diff --git a/git.c b/git.c
index 7e65323..cbc72d0 100644
--- a/git.c
+++ b/git.c
@@ -587,6 +587,93 @@ git_repo *get_repo(git_repo **repos, const char *name) {
 	return NULL;
 }
 
+int create_pull_request_branch(pull_request *pr, index_t *idx, git_repo *repo) {
+	int ret = 0;
+
+	/* Is this a NULL PR? */
+	if (pr == NULL) {
+		log(LOG_ERR, "Pull Request is NULL.");
+		return -1;
+	} else {
+		/* Prepend "pr" to the index path to create the PR branch index. */
+		char *pr_branch_index = make_index_path("pr", idx, 0);
+
+		/* Is the PR branch index empty? */
+		if (is_empty(pr_branch_index)) {
+			log(LOG_ERR, "Empty PR branch index.");
+			return -1;
+		} else {
+			/* Create the PR branch by just using the PR branch index. */
+			char *pr_branch = pr_branch_index;
+			/* Are we using a remote branch, and is the name of that branch non-empty? */
+			if (pr->pr_type && !is_empty(pr->branch->name)) {
+				/* Append the branch name to the PR branch index. */
+				pr_branch = dir_path_name((const char *)pr_branch_index, pr->branch->name);
+				/* Free the PR branch index */
+				free(pr_branch_index);
+			}
+			/* Is repo non-NULL, and the git repo non-NULL? */
+			if (repo != NULL && repo->repo != NULL) {
+				/* Are we using a remote branch? */
+				if (pr->pr_type) {
+					git_branch *branch = pr->branch;
+					/* Is the remote repo's URL non-empty? */
+					if (!is_empty(branch->repo)) {
+						git_remote *remote;
+						/* Did we successfully create the anonymous remote? */
+						if (!git_remote_create_anonymous(&remote, repo->repo, branch->repo)) {
+							char *branch_name = branch->name;
+							char *refspec;
+							const git_strarray refspecs = {&refspec, 1};
+							/* Is the branch name empty? */
+							if (is_empty(branch->name)) {
+								git_buf default_branch = {0};
+								log(LOG_WARNING, "Empty remote repo branch name, using default remote branch instead.");
+								/* Did we successfully get the default remote branch? */
+								if (!git_remote_default_branch(&default_branch, remote)) {
+									branch_name = default_branch.ptr;
+								} else {
+									log(LOG_ERR, "Failed to get default branch of remote repo \"%s\".", branch->repo);
+									free(pr_branch);
+									return -1;
+								}
+							}
+
+							refspec = calloc(format_len("%s:%s", branch_name, pr_branch)+1, sizeof(char));
+							sprintf(refspec, "%s:%s", branch_name, pr_branch);
+
+							/* Did we successfully fetch the remote repo? */
+							if (!git_remote_fetch(remote, &refspecs, NULL, NULL)) {
+								log(LOG_NOTICE, "Successfully fetched branch \"%s\" of remote repo \"%s\" into branch \"%s\".", branch_name, branch->repo, pr_branch);
+								ret = 0;
+							} else {
+								log(LOG_ERR, "Failed to fetch remote repo \"%s\".", branch->repo);
+								ret = -1;
+							}
+
+							/* Did we actually use the default remote branch? */
+							if (branch_name != branch->name) {
+								free(branch_name);
+							}
+							free(refspec);
+							free(pr_branch);
+							return ret;
+						} else {
+							log(LOG_ERR, "Failed to create anonymous remote for remote repo \"%s\".", branch->repo);
+							free(pr_branch);
+							return -1;
+						}
+					}
+				}
+			} else {
+				log(LOG_ERR, "Git repo is NULL.");
+				free(pr_branch);
+				return -1;
+			}
+		}
+	}
+}
+
 int create_pull_request_dir(pull_request *pr, index_t *idx, const char *root, const char *repo) {
 	int ret = 0;
 	struct stat st;
diff --git a/git.h b/git.h
index 595f7a5..e2c6776 100644
--- a/git.h
+++ b/git.h
@@ -56,6 +56,7 @@ extern git_repo **init_git(config *cfg);
 extern pull_request *get_pull_request(index_t *idx, const char *root, const char *repo);
 extern int add_comment(comment *comment, const char *pr_root);
 extern git_repo *get_repo(git_repo **repos, const char *name);
+extern int create_pull_request_branch(pull_request *pr, index_t *idx, git_repo *repo);
 extern int create_pull_request_dir(pull_request *pr, index_t *idx, const char *root, const char *repo);
 
 int parse_remote_branch(void *ctx, void *ret, const keyword *key, keyword_val val);