[workflow] Improve PR title checker for the release tag (#1244)

* [skip ci] [workflow] Improve PR title checker for the release tag

* [skip ci] enforce code format

* [skip ci] Apply suggestions from code review

Co-authored-by: Yuanming Hu <yuanming-hu@users.noreply.github.com>

Co-authored-by: Taichi Gardener <taichigardener@gmail.com>
Co-authored-by: Yuanming Hu <yuanming-hu@users.noreply.github.com>

.github/workflows/persubmit.yml

@@ -81,6 +81,7 @@ jobs:
 
       - name: Run PR Title Checker
         run: |
+          pip install semver GitPython
           python misc/check_pr_title.py "$PR_TITLE"
         env:
           PR_TITLE: ${{ github.event.pull_request.title }}

misc/check_pr_title.py

@@ -1,4 +1,18 @@
-import sys, os, json
+import sys, os, json, semver, git
+
+
+def get_old_ver():
+    repo = git.Repo('.')
+    for c in repo.iter_commits('master', max_count=200):
+        if c.summary.startswith('[release]'):
+            ver = c.summary.split(']', maxsplit=1)[1]
+            if ver[0] == 'v':
+                ver = ver[1:]
+            ver = ver.split(' ')[0]
+            oldver = semver.VersionInfo.parse(ver)
+            return oldver
+    raise ValueError('Could not find an old version!')
+
 
 title = sys.argv[1]
 print(f'Checking PR title: {title}')
@@ -26,10 +40,6 @@
     if x[1] == ' ':
         exit(f'Extra space before: {x[2:]}')
 
-x = title.split(']')[-1].strip()
-if x[0].islower():
-    exit(f'PR title should be uppercase at: {x}')
-
 had_upper = False
 for x in title.split('] ')[:-1]:
     if x[0] != '[':
@@ -43,4 +53,32 @@
             exit(f'At most 1 uppercase tag expected, got: [{x[1:]}]')
         had_upper = True
 
+is_release = False
+for x in title.split('] ')[:-1]:
+    x = x[1:]
+    if x.lower() == 'release':
+        is_release = True
+        if not x.islower():
+            exit(f'[release] must be lowercase, got: [{x}]')
+
+if is_release:
+    ts = title.split(']')
+    if len(ts) != 2:
+        exit(f'Release PRs must have only one tag "[release]", got: {title}')
+    ver = ts[1][1:]
+    if ver[0] != 'v':
+        exit(f'Release version must start with "v", got: {ver}')
+    ver = ver[1:]
+    try:
+        ver = semver.VersionInfo.parse(ver)
+    except ValueError:
+        exit(f'Invalid SemVer version: {ver}')
+    oldver = get_old_ver()
+    if ver not in [oldver.bump_minor(), oldver.bump_patch()]:
+        exit(f'Version bump incorrect: {oldver} -> {ver}')
+else:
+    x = title.split(']')[-1].strip()
+    if x[0].islower():
+        exit(f'PR titles must start with uppercase letters: {x}')
+
 print('OK!')