Support GPG signing in revup

docs/revup.md

@@ -98,6 +98,18 @@ expressions that match all possible base branches. Used to determine
 which branches are supported by base branch detection. See manpage of
 git-for-each-ref/fnmatch(3) for more info on glob syntax.
 
+**--gpg-sign, --no-gpg-sign**
+: Sign commits that revup creates internally (cherry-picks, synthetic
+commits, and virtual diff targets) with GPG or SSH. This is required
+for repositories that enforce verified-signature rules on pushed
+branches. If not specified, the value of `git config commit.gpgSign`
+is used. Signing uses the key configured by `user.signingKey` and
+the format from `gpg.format`.
+
+Note: `git commit-tree` (the plumbing command revup uses to create
+commits) intentionally ignores `commit.gpgSign`, which is why revup
+must read it explicitly and pass `-S` itself.
+
 # REVUP COMMANDS
 
 Revup is comprised of several sub-commands.

revup/git.py

@@ -135,6 +135,7 @@ async def make_git(
     base_branch_globs: str = "",
     keep_temp: bool = False,
     editor: str = "",
+    gpg_sign: Optional[bool] = None,
 ) -> "Git":
     if not git_path:
         git_path = get_default_git()
@@ -157,6 +158,12 @@ async def get_editor() -> str:
             ret = os.environ.get("GIT_EDITOR", os.environ.get("EDITOR", "nano"))
         return ret
 
+    async def get_gpg_sign() -> bool:
+        if gpg_sign is not None:
+            return gpg_sign
+        val = await git_ctx.git_stdout("config", "--get", "commit.gpgSign", raiseonerror=False)
+        return val.strip().lower() in ("true", "yes", "on", "1")
+
     (
         repo_root,
         git_dir,
@@ -172,6 +179,7 @@ async def get_editor() -> str:
         get_editor(),
         git_ctx.is_branch_or_commit(f"{remote_name}/{main_branch}"),
     )
+    gpg_sign_enabled = await get_gpg_sign()
 
     if git_version:
         version_arr = [int(v) for v in git_version.split(".")]
@@ -190,6 +198,7 @@ async def get_editor() -> str:
     git_ctx.email = email.lower()
     git_ctx.author = git_ctx.email.split("@")[0]
     git_ctx.editor = editor
+    git_ctx.gpg_sign = gpg_sign_enabled
     if not main_exists:
         if main_branch in COMMON_MAIN_BRANCHES:
             git_ctx.main_branch = COMMON_MAIN_BRANCHES[1 - COMMON_MAIN_BRANCHES.index(main_branch)]
@@ -230,6 +239,7 @@ class Git:
     email: str
     author: str
     editor: str
+    gpg_sign: bool
 
     def __init__(
         self,
@@ -245,6 +255,7 @@ def __init__(
         self.remote_name = remote_name
         self.keep_temp = keep_temp
         self.main_branch = main_branch
+        self.gpg_sign = False
         self.base_branch_globs = base_branch_globs.strip().splitlines()
         self.temp_dir = tempfile.TemporaryDirectory(  # pylint: disable=consider-using-with
             prefix="revup_"
@@ -580,6 +591,10 @@ async def commit_tree(self, commit_info: CommitHeader) -> GitCommitHash:
             "-m",
             commit_info.commit_msg,
         ]
+        if self.gpg_sign:
+            # git commit-tree (a plumbing command) intentionally ignores
+            # commit.gpgSign, so we pass -S explicitly when signing is enabled.
+            commit_tree_args.insert(2, "-S")
         for p in commit_info.parents:
             commit_tree_args.extend(["-p", p])
         ret = await self.git_stdout(*commit_tree_args, env=git_env)

revup/revup.py

@@ -62,6 +62,7 @@ def make_toplevel_parser() -> RevupArgParser:
     revup_parser.add_argument("--main-branch", default="main")
     revup_parser.add_argument("--base-branch-globs", default="")
     revup_parser.add_argument("--git-version", default="2.43.0")
+    revup_parser.add_argument("--gpg-sign", action="store_true", default=None)
     for s in ShellType:
         revup_parser.add_argument(
             f"--prompt-completion-{s.value}", default="", help=argparse.SUPPRESS
@@ -107,6 +108,7 @@ async def get_git(args: argparse.Namespace) -> git.Git:
         args.base_branch_globs,
         args.keep_temp,
         args.editor,
+        args.gpg_sign,
     )
 
     return git_ctx

tests/test_gpg.py

@@ -0,0 +1,81 @@
+from git_env import GitTestEnvironment, async_test
+
+from revup import git
+
+
+async def _set_gpg_config(env, value):
+    await env.sh.sh(env._git_path, "config", "commit.gpgSign", value)
+
+
+async def _make_git_in_env(env, gpg_sign=None):
+    return await git.make_git(
+        env.sh,
+        git_path=env._git_path,
+        remote_name="origin",
+        main_branch="main",
+        editor="true",
+        gpg_sign=gpg_sign,
+    )
+
+
+class TestMakeGitGpgSign:
+    @async_test
+    async def test_reads_from_git_config_true(self):
+        async with GitTestEnvironment() as env:
+            await _set_gpg_config(env, "true")
+            git_ctx = await _make_git_in_env(env)
+            assert git_ctx.gpg_sign is True
+
+    @async_test
+    async def test_reads_from_git_config_false(self):
+        async with GitTestEnvironment() as env:
+            await _set_gpg_config(env, "false")
+            git_ctx = await _make_git_in_env(env)
+            assert git_ctx.gpg_sign is False
+
+    @async_test
+    async def test_cli_override_true_when_config_unset(self):
+        async with GitTestEnvironment() as env:
+            git_ctx = await _make_git_in_env(env, gpg_sign=True)
+            assert git_ctx.gpg_sign is True
+
+    @async_test
+    async def test_cli_override_false_wins_over_config(self):
+        async with GitTestEnvironment() as env:
+            await _set_gpg_config(env, "true")
+            git_ctx = await _make_git_in_env(env, gpg_sign=False)
+            assert git_ctx.gpg_sign is False
+
+
+class TestCommitTreeSigning:
+    async def _get_real_commit_header(self, env):
+        commit_hash = await env.commit("base", {"a.txt": "hello"})
+        raw = await env.git_ctx.rev_list(commit_hash, max_revs=1, header=True)
+        return git.parse_rev_list(raw)[0]
+
+    async def _capture_commit_tree_args(self, env, gpg_sign, mocker):
+        commit_info = await self._get_real_commit_header(env)
+        env.git_ctx.gpg_sign = gpg_sign
+
+        async def fake_git_stdout(*args, **kwargs):
+            return "fakecommithash"
+
+        spy = mocker.patch.object(env.git_ctx, "git_stdout", side_effect=fake_git_stdout)
+
+        result = await env.git_ctx.commit_tree(commit_info)
+        assert result == "fakecommithash"
+        return spy.call_args.args
+
+    @async_test
+    async def test_dash_s_present_when_gpg_sign_enabled(self, mocker):
+        async with GitTestEnvironment() as env:
+            args = await self._capture_commit_tree_args(env, True, mocker)
+            assert "commit-tree" in args
+            assert "-S" in args
+
+    @async_test
+    async def test_dash_s_absent_when_gpg_sign_disabled(self, mocker):
+        async with GitTestEnvironment() as env:
+            args = await self._capture_commit_tree_args(env, False, mocker)
+            assert "commit-tree" in args
+            assert "-S" not in args