Fix CI logic for PRs run against external forks. [ci skip]

Author: lohedges

.github/workflows/pr.yaml

@@ -45,6 +45,7 @@ jobs:
       SIRE_SILENT_PHONEHOME: 1
       SIRE_EMLE: 1
       REPO: "${{ github.event.pull_request.head.repo.full_name || github.repository }}"
+      SIRE_REMOTE: "https://github.com/${{ github.event.pull_request.head.repo.full_name || github.repository }}.git"
     steps:
       #
       - uses: actions/checkout@v4

actions/generate_recipe.py

@@ -91,11 +91,20 @@ def get_git_info(srcdir):
     """Get the git remote URL and branch/tag."""
     gitdir = os.path.join(srcdir, ".git")
 
-    remote = run_cmd(
-        f"git --git-dir={gitdir} --work-tree={srcdir} config --get remote.origin.url"
-    )
-    if not remote.endswith(".git"):
-        remote += ".git"
+    # For PR builds from external forks the checkout remote points to the base
+    # repo, not the fork.  The workflow sets SIRE_REMOTE to the fork's clone
+    # URL so that rattler-build fetches from the right place.
+    env_remote = os.environ.get("SIRE_REMOTE")
+    if env_remote:
+        remote = env_remote
+        if not remote.endswith(".git"):
+            remote += ".git"
+    else:
+        remote = run_cmd(
+            f"git --git-dir={gitdir} --work-tree={srcdir} config --get remote.origin.url"
+        )
+        if not remote.endswith(".git"):
+            remote += ".git"
 
     branch = run_cmd(
         f"git --git-dir={gitdir} --work-tree={srcdir} rev-parse --abbrev-ref HEAD"