Improve changelog generation script

RELEASES.md

@@ -84,6 +84,7 @@ I usually do this all on the `master` branch, but doing it in a release branch i
 (cd crates/egui_demo_lib        && cargo publish --quiet)  &&  echo "✅ egui_demo_lib"
 (cd crates/egui_glow            && cargo publish --quiet)  &&  echo "✅ egui_glow"
 (cd crates/eframe               && cargo publish --quiet)  &&  echo "✅ eframe"
+(cd crates/egui_kittest         && cargo publish --quiet)  &&  echo "✅ egui_kittest"
 ```
 
 ## Announcements

scripts/generate_changelog.py

@@ -214,18 +214,42 @@ def add_to_changelog_file(crate: str, content: str, version: str) -> None:
         file.write(content)
 
 
+def calc_commit_range(new_version: str) -> str:
+    parts = new_version.split(".")
+    assert len(parts) == 3, "Expected version to be on the format X.Y.Z"
+    major = int(parts[0])
+    minor = int(parts[1])
+    patch = int(parts[2])
+
+    if 0 < patch:
+        # A patch release.
+        # Include changes since last patch release.
+        # This assumes we've cherry-picked stuff for this release.
+        diff_since_version = f"0.{minor}.{patch - 1}"
+    elif 0 < minor:
+        # A minor release
+        # The diff should span everything since the last minor release.
+        # The script later excludes duplicated automatically, so we don't include stuff that
+        # was part of intervening patch releases.
+        diff_since_version = f"{major}.{minor - 1}.0"
+    else:
+        # A major release
+        # The diff should span everything since the last major release.
+        # The script later excludes duplicated automatically, so we don't include stuff that
+        # was part of intervening minor/patch releases.
+        diff_since_version = f"{major - 1}.{minor}.0"
+
+    return f"{diff_since_version}..HEAD"
+
+
 def main() -> None:
     parser = argparse.ArgumentParser(description="Generate a changelog.")
-    parser.add_argument("--commit-range", help="e.g. 0.24.0..HEAD", required=True)
+    parser.add_argument("--version", help="What release is this?", required=True)
     parser.add_argument(
         "--write", help="Write into the different changelogs?", action="store_true"
     )
-    parser.add_argument("--version", help="What release is this?")
     args = parser.parse_args()
-
-    if args.write and not args.version:
-        print("ERROR: --version is required when --write is used")
-        sys.exit(1)
+    commit_range = calc_commit_range(args.version)
 
     crate_names = [
         "ecolor",
@@ -251,7 +275,7 @@ def main() -> None:
             all_changelogs += file.read()
 
     repo = Repo(".")
-    commits = list(repo.iter_commits(args.commit_range))
+    commits = list(repo.iter_commits(commit_range))
     commits.reverse()  # Most recent last
     commit_infos = list(map(get_commit_info, commits))
 
@@ -307,7 +331,7 @@ def main() -> None:
                     unsorted_prs.append(pr_summary(pr_info))
 
     print()
-    print(f"Full diff at https://github.com/emilk/egui/compare/{args.commit_range}")
+    print(f"Full diff at https://github.com/emilk/egui/compare/{commit_range}")
     print()
     for crate in crate_names:
         if crate in crate_sections: