Parse PR number directly (#263)

Author: vmoens

README.md

@@ -51,7 +51,8 @@ branch, and start working on a fresh branch.
 
 **WARNING.**  You will NOT be able to merge these commits using the
 normal GitHub UI, as their branch bases won't be master.  Use
-`ghstack land $PR_URL` to land a ghstack'ed pull request.
+`ghstack land $PR_URL` (or alternatively `ghtstack land #PR_NUM`) to land
+a ghstack'ed pull request.
 
 ## Structure of submitted pull requests
 

ghstack/github_utils.py

@@ -115,9 +115,23 @@ def get_github_repo_info(
 )
 
 
-def parse_pull_request(pull_request: str) -> GitHubPullRequestParams:
+def parse_pull_request(
+    pull_request: str,
+    *,
+    sh: Optional[ghstack.shell.Shell] = None,
+    remote_name: Optional[str] = None,
+) -> GitHubPullRequestParams:
     m = RE_PR_URL.match(pull_request)
     if not m:
+        # We can reconstruct the URL if just a PR number is passed
+        if sh is not None and remote_name is not None:
+            remote_url = sh.git("remote", "get-url", remote_name)
+            # Do not pass the shell to avoid infinite loop
+            try:
+                return parse_pull_request(remote_url + "/pull/" + pull_request)
+            except RuntimeError:
+                # Fall back on original error message
+                pass
         raise RuntimeError("Did not understand PR argument.  PR must be URL")
 
     github_url = m.group("github_url")

ghstack/land.py

@@ -57,7 +57,9 @@ def main(
     # Furthermore, the parent commits of PR are ignored: we always
     # take the canonical version of the patch from any given pr
 
-    params = ghstack.github_utils.parse_pull_request(pull_request)
+    params = ghstack.github_utils.parse_pull_request(
+        pull_request, sh=sh, remote_name=remote_name
+    )
     default_branch = ghstack.github_utils.get_github_repo_info(
         github=github,
         sh=sh,