amend: Refresh committer date

revup/amend.py

@@ -211,7 +211,8 @@ async def rebuild_stack_last_touched(
             amended.author_date = commit_obj.author_date
             amended.committer_name = commit_obj.committer_name
             amended.committer_email = commit_obj.committer_email
-            amended.committer_date = commit_obj.committer_date
+            # Refresh committer date, like git commit --amend.
+            amended.committer_date = ""
             amended.commit_msg = commit_obj.commit_msg
             new_commit = await git_ctx.commit_tree(amended)
         else:
@@ -319,6 +320,9 @@ async def get_has_unstaged() -> bool:
     if len(stack) == 0:
         raise RevupUsageException(f"Couldn't find any commits between HEAD and {commit}~")
 
+    # Refresh the amended commit's committer date, like git commit --amend.
+    stack[0].committer_date = ""
+
     if args.insert:
         # Create a new empty commit after the given commit
         stack[0].parents = [stack[0].commit_id]

tests/git_env.py

@@ -97,15 +97,15 @@ async def write_file(self, name, content):
     async def read_file(self, name):
         return (self.tmp_dir / name).read_text()
 
-    async def commit(self, message, files=None):
+    async def commit(self, message, files=None, committer_date=None):
         if files:
             for name, content in files.items():
                 await self.write_file(name, content)
                 await self.git_ctx.git("add", name)
         ts = self._next_timestamp()
         env = {
             "GIT_AUTHOR_DATE": ts,
-            "GIT_COMMITTER_DATE": ts,
+            "GIT_COMMITTER_DATE": committer_date if committer_date is not None else ts,
         }
         await self.git_ctx.git("commit", "-m", message, "--allow-empty", env=env)
         self.commit_count += 1
@@ -121,6 +121,12 @@ async def get_commit_message(self, ref="HEAD"):
     async def get_commit_hash(self, ref="HEAD"):
         return GitCommitHash(await self.git_ctx.git_stdout("rev-parse", ref))
 
+    async def get_author_date(self, ref="HEAD"):
+        return await self.git_ctx.git_stdout("log", "-1", "--format=%at", ref)
+
+    async def get_committer_date(self, ref="HEAD"):
+        return await self.git_ctx.git_stdout("log", "-1", "--format=%ct", ref)
+
     async def get_file_at_commit(self, name, ref="HEAD"):
         return await self.git_ctx.git_stdout("show", f"{ref}:{name}")
 

tests/test_amend.py

@@ -645,6 +645,61 @@ async def test_amend_changes_commit_hashes(self):
             assert new_head != orig_head
 
 
+class TestAmendCommitterDate:
+    @async_test
+    async def test_amend_refreshes_committer_date_preserves_author(self):
+        async with GitTestEnvironment() as env:
+            await env.commit("root", {"root.txt": "r"})
+            # Epoch 0 so any refresh is strictly greater
+            await env.commit("first", {"a.txt": "a"}, committer_date="@0 +0000")
+            orig_author = await env.get_author_date()
+
+            await env.stage_file("a.txt", "modified")
+            args = make_amend_args(edit=False)
+            ret = await amend.main(args, env.git_ctx)
+
+            assert ret == 0
+            assert await env.get_author_date() == orig_author
+            assert int(await env.get_committer_date()) > 0
+
+    @async_test
+    async def test_amend_earlier_commit_refreshes_committer_date(self):
+        async with GitTestEnvironment() as env:
+            await env.commit("root", {"root.txt": "r"})
+            await env.commit("first", {"a.txt": "a"}, committer_date="@0 +0000")
+            await env.commit("second", {"b.txt": "b"})
+            orig_author = await env.get_author_date("HEAD~1")
+            top_committer = await env.get_committer_date("HEAD")
+
+            await env.stage_file("a.txt", "modified")
+            args = make_amend_args(ref_or_topic="HEAD~1", edit=False)
+            ret = await amend.main(args, env.git_ctx)
+
+            assert ret == 0
+            assert await env.get_author_date("HEAD~1") == orig_author
+            assert int(await env.get_committer_date("HEAD~1")) > 0
+            # Recreated commit keeps its date
+            assert await env.get_committer_date("HEAD") == top_committer
+
+    @async_test
+    async def test_last_touched_refreshes_committer_date(self):
+        async with GitTestEnvironment() as env:
+            await env.commit("root", {"root.txt": "r"})
+            await env.git_ctx.git("branch", "origin/main", "HEAD")
+            # Old but valid timestamp; the refresh must move committer date past it.
+            await env.commit(
+                "first\n\nTopic: alpha", {"a.txt": "v1"}, committer_date="@1000000000 +0000"
+            )
+            orig_author = await env.get_author_date("HEAD")
+
+            await env.stage_file("a.txt", "v2")
+            args = make_amend_args(last_touched=True, parse_topics=True)
+            await amend.main(args, env.git_ctx)
+
+            assert await env.get_author_date("HEAD") == orig_author
+            assert int(await env.get_committer_date("HEAD")) > 1000000000
+
+
 class TestAmendSingleCommit:
     @async_test
     async def test_amend_only_commit_above_root(self):