release.sh: better list dependency changes

Instead of a dumb diff, add a script to render a pretty list of changed
dependency versions.

Separate the new and removed dependencies from the version updates.

Signed-off-by: Robin Jarry <robin@jarry.cc>

2 files changed, 101 insertions, 1 deletions

diff --git a/contrib/depends-diff.py b/contrib/depends-diff.py
new file mode 100755
index 00000000..3bccf3de
--- /dev/null
+++ b/contrib/depends-diff.py
@@ -0,0 +1,100 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: MIT
+# Copyright (c) 2024 Robin Jarry
+
+import argparse
+import re
+import subprocess
+
+DEP_CHANGE_RE = re.compile(
+    r"""
+    ^
+    (?P<diff>[\+\-])\s*
+    (?P<name>\S+)\s*
+    (?P<version>v\S+)\s*
+    (?://\s*indirect)?
+    $
+    """,
+    re.VERBOSE,
+)
+REPLACE_RE = re.compile(
+    r"""
+    ^
+    (?P<diff>[\+\-])\s*
+    replace
+    (?P<name>\S+)\s*
+    =>\s*
+    (?P<replacement>\S+)\s*
+    (?P<version>v\S+)\s*
+    $
+    """,
+    re.VERBOSE,
+)
+
+
+def main():
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument(
+        "git_range",
+        metavar="GIT_RANGE",
+        help="The git revision range (see gitrevisions(7)).",
+    )
+    args = parser.parse_args()
+
+    old_deps = {}
+    new_deps = {}
+
+    with subprocess.Popen(
+        ["git", "diff", "-U0", "--ignore-all-space", args.git_range, "--", "go.mod"],
+        stdout=subprocess.PIPE,
+        encoding="utf-8",
+    ) as proc:
+        for line in proc.stdout:
+            match = DEP_CHANGE_RE.match(line.strip())
+            if not match:
+                match = REPLACE_RE.match(line.strip())
+                if not match:
+                    continue
+                diff, name, replacement, version = match.groups()
+                if diff == "+":
+                    new_deps[replacement] = version
+                    del new_deps[name]
+                continue
+            diff, name, version = match.groups()
+            if diff == "+":
+                new_deps[name] = version
+            else:
+                old_deps[name] = version
+
+    print("## New")
+    print()
+    added = new_deps.keys() - old_deps.keys()
+    if added:
+        for a in sorted(added):
+            print("+", a, new_deps[a])
+    else:
+        print("none")
+
+    print()
+    print("## Updated")
+    print()
+    updated = old_deps.keys() & new_deps.keys()
+    if updated:
+        for u in sorted(updated):
+            print("*", u, old_deps[u], "=>", new_deps[u])
+    else:
+        print("none")
+
+    print()
+    print("## Removed")
+    print()
+    removed = old_deps.keys() - new_deps.keys()
+    if removed:
+        for r in sorted(removed):
+            print("-", r)
+    else:
+        print("none")
+
+
+if __name__ == "__main__":
+    main()
diff --git a/contrib/release.sh b/contrib/release.sh
index 21d3d028..80049252 100755
--- a/contrib/release.sh
+++ b/contrib/release.sh
@@ -103,7 +103,7 @@ $(changelog '#')
 
 # Changed dependencies for downstream packagers
 
-$(git diff -U0 $prev_tag.. go.mod)
+$(contrib/depends-diff.py $prev_tag..)
 
 Thanks to all contributors!