Merge pull request #13 from secondlife/relnotes

For a tag build with a PR, make which-branch dig out relnotes.

Author: nat-goodspeed

which-branch/README.md

@@ -11,4 +11,4 @@ This is necessary for a release action because release actions are driven by a t
 | Output | Description |
 | ------ | ----------- |
 | branch | name of the branch whose tip is `github.sha`, or empty string |
-
+| relnotes | for a tag build, if the branch has a Pull Request, the release notes from the PR description |

which-branch/action.yaml

@@ -11,6 +11,9 @@ outputs:
   branch:
     description: "Branch whose tip is used for this build"
     value: ${{ steps.which-branch.outputs.branch }}
+  relnotes:
+    description: "For a tag build with a PR, PR description after 'relnotes:'"
+    value: ${{ steps.which-branch.outputs.relnotes }}
 
 runs:
   using: composite
@@ -25,10 +28,11 @@ runs:
             # For a pull request, GITHUB_HEAD_REF is the branch name.
             # For a branch build, GITHUB_REF_NAME is the branch name.
             branch="${GITHUB_HEAD_REF:-${GITHUB_REF_NAME}}"
+            echo "branch=$branch" >> "$GITHUB_OUTPUT"
         else
             # For a tag build, have to discover which branch corresponds.
             pip3 install PyGithub
-            branch="$(python '${{ github.action_path }}/which_branch.py' \
-                      -t "${{ inputs.token }}" -r "${{github.repository }}" "${{ github.sha }}")"
+            # which_branch.py sets output vars in GITHUB_OUTPUT
+            python '${{ github.action_path }}/which_branch.py' \
+                   -t "${{ inputs.token }}" -r "${{github.repository }}" "${{ github.sha }}"
         fi
-        echo "branch=$branch" >> "$GITHUB_OUTPUT"

which-branch/which_branch.py

@@ -10,7 +10,7 @@
 $/LicenseInfo$
 """
 
-import contextlib
+import os
 import re
 import subprocess
 import sys
@@ -22,7 +22,7 @@ class Error(Exception):
     pass
 
 
-def branches_for(token, commit, repo=None):
+def branches_for(repo, commit):
     """
     Use the GitHub REST API to discover which branch(es) correspond to the
     passed commit hash. The commit string can actually be any of the ways git
@@ -32,21 +32,10 @@ def branches_for(token, commit, repo=None):
 
     branches_for() generates a (possibly empty) sequence of all the branches
     of the specified repo for which the specified commit is the tip.
-
-    If repo is omitted or None, assume the current directory is a local clone
-    whose 'origin' remote is the GitHub repository of interest.
     """
-    if not repo:
-        url = subprocess.check_output(['git', 'remote', 'get-url', 'origin'],
-                                      text=True)
-        parts = re.split(r'[:/]', url.rstrip())
-        repo = '/'.join(parts[-2:]).removesuffix('.git')
-
-    gh = github.MainClass.Github(token)
-    grepo = gh.get_repo(repo)
-    for branch in grepo.get_branches():
+    for branch in repo.get_branches():
         try:
-            delta = grepo.compare(base=commit, head=branch.name)
+            delta = repo.compare(base=commit, head=branch.name)
         except github.GithubException:
             continue
 
@@ -70,10 +59,59 @@ def main(*raw_args):
                         help="""GitHub repository name, in the form OWNER/REPOSITORY""")
     parser.add_argument('commit',
                         help="""commit hash at the tip of the sought branch""")
-
     args = parser.parse_args(raw_args)
-    with contextlib.suppress(StopIteration):
-        print(next(iter(branches_for(token=args.token, commit=args.commit, repo=args.repo))).name)
+
+    # If repo is omitted or None, assume the current directory is a local clone
+    # whose 'origin' remote is the GitHub repository of interest.
+    if not args.repo:
+        url = subprocess.check_output(['git', 'remote', 'get-url', 'origin'],
+                                      text=True)
+        parts = re.split(r'[:/]', url.rstrip())
+        args.repo = '/'.join(parts[-2:]).removesuffix('.git')
+
+    gh = github.MainClass.Github(args.token)
+    repo = gh.get_repo(args.repo)
+
+    try:
+        branch = next(iter(branches_for(repo=repo, commit=args.commit))).name
+    except StopIteration:
+        return
+
+    # If we weren't run as a GitHub action (no $GITHUB_OUTPUT), just show user
+    # output variables.
+    GITHUB_OUTPUT = os.getenv("GITHUB_OUTPUT")
+    if GITHUB_OUTPUT:
+        outf = open(GITHUB_OUTPUT, "a")
+    else:
+        outf = sys.stdout
+
+    print(f"branch={branch}", file=outf)
+
+    # Can we find a pull request corresponding to this branch?
+    # (Is there a better way than just searching PRs?)
+    # Empirically, although get_pulls(head=branch) would seem to do exactly
+    # what we want, we always end up with a list of all open PRs anyway.
+    try:
+        pr = next(pr for pr in repo.get_pulls(head=branch) if pr.head.ref == branch)
+    except StopIteration:
+        return
+
+    # pr.body is the PR's description. Look for a line embedded in that
+    # description containing only 'relnotes:'.
+    lines = iter(pr.body.splitlines())
+    try:
+        next(line for line in lines if line.strip() == 'relnotes:')
+    except StopIteration:
+        return
+
+    # Having found that line, the rest of the body is the release notes
+    # header.
+    outf.writelines((
+        'relnotes<<EOF\n',
+        '\n'.join(lines),
+        '\n',
+        'EOF\n'
+    ))
 
 
 if __name__ == "__main__":