[PATCH 1/3] builtin/history: sign rewritten commits

[Souma <git@5ouma.me>]

The history commands create replacement commits directly instead of
using the sequencer or the commit porcelain. As a result, rewritten
commits ignore commit.gpgsign and cannot be signed on demand.

Read the usual signing configuration before parsing history options.
Add the commit-style -S/--gpg-sign knob, and pass the selected
signing key through direct rewrites and replayed descendants.

Signed-off-by: Souma <git@5ouma.me>
---
 builtin/history.c | 80 ++++++++++++++++++++++++++++++++++++-----------
 replay.c          | 13 +++++---
 replay.h          |  6 ++++
 3 files changed, 76 insertions(+), 23 deletions(-)

diff --git a/builtin/history.c b/builtin/history.c
index 091465a59e..8d669cf539 100644
--- a/builtin/history.c
+++ b/builtin/history.c
@@ -25,11 +25,11 @@
 #include "wt-status.h"
 
 #define GIT_HISTORY_FIXUP_USAGE \
-	N_("git history fixup <commit> [--dry-run] [--update-refs=(branches|head)] [--reedit-message] [--empty=(drop|keep|abort)]")
+	N_("git history fixup <commit> [--dry-run] [--update-refs=(branches|head)] [--reedit-message] [--empty=(drop|keep|abort)] [--[no-]gpg-sign[=<key-id>]]")
 #define GIT_HISTORY_REWORD_USAGE \
-	N_("git history reword <commit> [--dry-run] [--update-refs=(branches|head)]")
+	N_("git history reword <commit> [--dry-run] [--update-refs=(branches|head)] [--[no-]gpg-sign[=<key-id>]]")
 #define GIT_HISTORY_SPLIT_USAGE \
-	N_("git history split <commit> [--dry-run] [--update-refs=(branches|head)] [--] [<pathspec>...]")
+	N_("git history split <commit> [--dry-run] [--update-refs=(branches|head)] [--[no-]gpg-sign[=<key-id>]] [--] [<pathspec>...]")
 
 static void change_data_free(void *util, const char *str UNUSED)
 {
@@ -98,6 +98,30 @@ enum commit_tree_flags {
 	COMMIT_TREE_EDIT_MESSAGE = (1 << 0),
 };
 
+static int history_config(const char *var, const char *value,
+			  const struct config_context *ctx, void *data)
+{
+	const char **sign_commit = data;
+
+	if (!strcmp(var, "commit.gpgsign")) {
+		*sign_commit = git_config_bool(var, value) ? "" : NULL;
+		return 0;
+	}
+
+	return git_default_config(var, value, ctx, data);
+}
+
+#define OPT_HISTORY_GPG_SIGN(v) { \
+	.type = OPTION_STRING, \
+	.short_name = 'S', \
+	.long_name = "gpg-sign", \
+	.value = (v), \
+	.argh = N_("key-id"), \
+	.help = N_("GPG-sign rewritten commits"), \
+	.flags = PARSE_OPT_OPTARG, \
+	.defval = (intptr_t) "", \
+}
+
 static int commit_tree_ext(struct repository *repo,
 			   const char *action,
 			   struct commit *commit_with_message,
@@ -105,6 +129,7 @@ static int commit_tree_ext(struct repository *repo,
 			   const struct object_id *old_tree,
 			   const struct object_id *new_tree,
 			   struct commit **out,
+			   const char *sign_commit,
 			   enum commit_tree_flags flags)
 {
 	const char *exclude_gpgsig[] = {
@@ -144,7 +169,7 @@ static int commit_tree_ext(struct repository *repo,
 
 	ret = commit_tree_extended(commit_message.buf, commit_message.len, new_tree,
 				   parents, &rewritten_commit_oid, original_author,
-				   NULL, NULL, original_extra_headers);
+				   NULL, sign_commit, original_extra_headers);
 	if (ret < 0)
 		goto out;
 
@@ -160,7 +185,8 @@ static int commit_tree_ext(struct repository *repo,
 static int commit_tree_with_edited_message(struct repository *repo,
 					   const char *action,
 					   struct commit *original,
-					   struct commit **out)
+					   struct commit **out,
+					   const char *sign_commit)
 {
 	struct object_id parent_tree_oid;
 	const struct object_id *tree_oid;
@@ -181,7 +207,8 @@ static int commit_tree_with_edited_message(struct repository *repo,
 	}
 
 	return commit_tree_ext(repo, action, original, original->parents,
-			       &parent_tree_oid, tree_oid, out, COMMIT_TREE_EDIT_MESSAGE);
+			       &parent_tree_oid, tree_oid, out, sign_commit,
+			       COMMIT_TREE_EDIT_MESSAGE);
 }
 
 enum ref_action {
@@ -339,11 +366,13 @@ static int handle_reference_updates(struct rev_info *revs,
 				    struct commit *rewritten,
 				    const char *reflog_msg,
 				    int dry_run,
+				    const char *sign_commit,
 				    enum replay_empty_commit_action empty)
 {
 	const struct name_decoration *decoration;
 	struct replay_revisions_options opts = {
 		.empty = empty,
+		.sign_commit = sign_commit,
 	};
 	struct replay_result result = { 0 };
 	struct ref_transaction *transaction = NULL;
@@ -491,6 +520,7 @@ static int cmd_history_fixup(int argc,
 	enum replay_empty_commit_action empty = REPLAY_EMPTY_COMMIT_DROP;
 	enum ref_action action = REF_ACTION_DEFAULT;
 	enum commit_tree_flags flags = 0;
+	const char *sign_commit = NULL;
 	int dry_run = 0;
 	struct option options[] = {
 		OPT_CALLBACK_F(0, "update-refs", &action, "(branches|head)",
@@ -504,6 +534,7 @@ static int cmd_history_fixup(int argc,
 		OPT_CALLBACK_F(0, "empty", &empty, "(drop|keep|abort)",
 			       N_("how to handle commits that become empty"),
 			       PARSE_OPT_NONEG, parse_opt_empty),
+		OPT_HISTORY_GPG_SIGN(&sign_commit),
 		OPT_END(),
 	};
 	struct merge_result merge_result = { 0 };
@@ -515,12 +546,13 @@ static int cmd_history_fixup(int argc,
 	bool skip_commit = false;
 	int ret;
 
+	repo_config(repo, history_config, &sign_commit);
+
 	argc = parse_options(argc, argv, prefix, options, usage, 0);
 	if (argc != 1) {
 		ret = error(_("command expects a single revision"));
 		goto out;
 	}
-	repo_config(repo, git_default_config, NULL);
 
 	if (action == REF_ACTION_DEFAULT)
 		action = REF_ACTION_BRANCHES;
@@ -645,7 +677,7 @@ static int cmd_history_fixup(int argc,
 	if (!skip_commit) {
 		ret = commit_tree_ext(repo, "fixup", original, original->parents,
 				      &original_tree->object.oid, &merge_result.tree->object.oid,
-				      &rewritten, flags);
+				      &rewritten, sign_commit, flags);
 		if (ret < 0) {
 			ret = error(_("failed writing fixed-up commit"));
 			goto out;
@@ -655,7 +687,7 @@ static int cmd_history_fixup(int argc,
 	strbuf_addf(&reflog_msg, "fixup: updating %s", argv[0]);
 
 	ret = handle_reference_updates(&revs, action, original, rewritten,
-				       reflog_msg.buf, dry_run, empty);
+				       reflog_msg.buf, dry_run, sign_commit, empty);
 	if (ret < 0) {
 		ret = error(_("failed replaying descendants"));
 		goto out;
@@ -680,6 +712,7 @@ static int cmd_history_reword(int argc,
 		NULL,
 	};
 	enum ref_action action = REF_ACTION_DEFAULT;
+	const char *sign_commit = NULL;
 	int dry_run = 0;
 	struct option options[] = {
 		OPT_CALLBACK_F(0, "update-refs", &action, "(branches|head)",
@@ -687,6 +720,7 @@ static int cmd_history_reword(int argc,
 			       PARSE_OPT_NONEG, parse_ref_action),
 		OPT_BOOL('n', "dry-run", &dry_run,
 			 N_("perform a dry-run without updating any refs")),
+		OPT_HISTORY_GPG_SIGN(&sign_commit),
 		OPT_END(),
 	};
 	struct strbuf reflog_msg = STRBUF_INIT;
@@ -694,12 +728,13 @@ static int cmd_history_reword(int argc,
 	struct rev_info revs = { 0 };
 	int ret;
 
+	repo_config(repo, history_config, &sign_commit);
+
 	argc = parse_options(argc, argv, prefix, options, usage, 0);
 	if (argc != 1) {
 		ret = error(_("command expects a single revision"));
 		goto out;
 	}
-	repo_config(repo, git_default_config, NULL);
 
 	if (action == REF_ACTION_DEFAULT)
 		action = REF_ACTION_BRANCHES;
@@ -714,7 +749,8 @@ static int cmd_history_reword(int argc,
 	if (ret)
 		goto out;
 
-	ret = commit_tree_with_edited_message(repo, "reworded", original, &rewritten);
+	ret = commit_tree_with_edited_message(repo, "reworded", original,
+					      &rewritten, sign_commit);
 	if (ret < 0) {
 		ret = error(_("failed writing reworded commit"));
 		goto out;
@@ -723,7 +759,8 @@ static int cmd_history_reword(int argc,
 	strbuf_addf(&reflog_msg, "reword: updating %s", argv[0]);
 
 	ret = handle_reference_updates(&revs, action, original, rewritten,
-				       reflog_msg.buf, dry_run, REPLAY_EMPTY_COMMIT_ABORT);
+				       reflog_msg.buf, dry_run, sign_commit,
+				       REPLAY_EMPTY_COMMIT_ABORT);
 	if (ret < 0) {
 		ret = error(_("failed replaying descendants"));
 		goto out;
@@ -785,7 +822,8 @@ static int write_ondisk_index(struct repository *repo,
 static int split_commit(struct repository *repo,
 			struct commit *original,
 			struct pathspec *pathspec,
-			struct commit **out)
+			struct commit **out,
+			const char *sign_commit)
 {
 	struct interactive_options interactive_opts = INTERACTIVE_OPTIONS_INIT;
 	struct strbuf index_file = STRBUF_INIT;
@@ -862,7 +900,8 @@ static int split_commit(struct repository *repo,
 	 * that shall be diffed against is the parent of the original commit.
 	 */
 	ret = commit_tree_ext(repo, "split-out", original, original->parents, &parent_tree_oid,
-			      &split_tree->object.oid, &first_commit, COMMIT_TREE_EDIT_MESSAGE);
+			      &split_tree->object.oid, &first_commit, sign_commit,
+			      COMMIT_TREE_EDIT_MESSAGE);
 	if (ret < 0) {
 		ret = error(_("failed writing first commit"));
 		goto out;
@@ -879,7 +918,8 @@ static int split_commit(struct repository *repo,
 	new_tree_oid = &repo_get_commit_tree(repo, original)->object.oid;
 
 	ret = commit_tree_ext(repo, "split-out", original, parents, old_tree_oid,
-			      new_tree_oid, &second_commit, COMMIT_TREE_EDIT_MESSAGE);
+			      new_tree_oid, &second_commit, sign_commit,
+			      COMMIT_TREE_EDIT_MESSAGE);
 	if (ret < 0) {
 		ret = error(_("failed writing second commit"));
 		goto out;
@@ -907,6 +947,7 @@ static int cmd_history_split(int argc,
 		NULL,
 	};
 	enum ref_action action = REF_ACTION_DEFAULT;
+	const char *sign_commit = NULL;
 	int dry_run = 0;
 	struct option options[] = {
 		OPT_CALLBACK_F(0, "update-refs", &action, "(branches|head)",
@@ -914,6 +955,7 @@ static int cmd_history_split(int argc,
 			       PARSE_OPT_NONEG, parse_ref_action),
 		OPT_BOOL('n', "dry-run", &dry_run,
 			 N_("perform a dry-run without updating any refs")),
+		OPT_HISTORY_GPG_SIGN(&sign_commit),
 		OPT_END(),
 	};
 	struct commit *original, *rewritten = NULL;
@@ -922,12 +964,13 @@ static int cmd_history_split(int argc,
 	struct rev_info revs = { 0 };
 	int ret;
 
+	repo_config(repo, history_config, &sign_commit);
+
 	argc = parse_options(argc, argv, prefix, options, usage, 0);
 	if (argc < 1) {
 		ret = error(_("command expects a committish"));
 		goto out;
 	}
-	repo_config(repo, git_default_config, NULL);
 
 	if (action == REF_ACTION_DEFAULT)
 		action = REF_ACTION_BRANCHES;
@@ -953,14 +996,15 @@ static int cmd_history_split(int argc,
 		goto out;
 	}
 
-	ret = split_commit(repo, original, &pathspec, &rewritten);
+	ret = split_commit(repo, original, &pathspec, &rewritten, sign_commit);
 	if (ret < 0)
 		goto out;
 
 	strbuf_addf(&reflog_msg, "split: updating %s", argv[0]);
 
 	ret = handle_reference_updates(&revs, action, original, rewritten,
-				       reflog_msg.buf, dry_run, REPLAY_EMPTY_COMMIT_ABORT);
+				       reflog_msg.buf, dry_run, sign_commit,
+				       REPLAY_EMPTY_COMMIT_ABORT);
 	if (ret < 0) {
 		ret = error(_("failed replaying descendants"));
 		goto out;
diff --git a/replay.c b/replay.c
index da531d5bc6..683c384ef8 100644
--- a/replay.c
+++ b/replay.c
@@ -81,13 +81,13 @@ static struct commit *create_commit(struct repository *repo,
 				    struct tree *tree,
 				    struct commit *based_on,
 				    struct commit *parent,
-				    enum replay_mode mode)
+				    enum replay_mode mode,
+				    const char *sign_commit)
 {
 	struct object_id ret;
 	struct object *obj = NULL;
 	struct commit_list *parents = NULL;
 	char *author = NULL;
-	char *sign_commit = NULL; /* FIXME: cli users might want to sign again */
 	struct commit_extra_header *extra = NULL;
 	struct strbuf msg = STRBUF_INIT;
 	const char *out_enc = get_commit_output_encoding();
@@ -270,7 +270,8 @@ static struct commit *pick_regular_commit(struct repository *repo,
 					  struct merge_options *merge_opt,
 					  struct merge_result *result,
 					  enum replay_mode mode,
-					  enum replay_empty_commit_action empty)
+					  enum replay_empty_commit_action empty,
+					  const char *sign_commit)
 {
 	struct commit *base, *replayed_base;
 	struct tree *pickme_tree, *base_tree, *replayed_base_tree;
@@ -341,7 +342,8 @@ static struct commit *pick_regular_commit(struct repository *repo,
 		}
 	}
 
-	return create_commit(repo, result->tree, pickme, replayed_base, mode);
+	return create_commit(repo, result->tree, pickme, replayed_base, mode,
+			     sign_commit);
 }
 
 void replay_result_release(struct replay_result *result)
@@ -431,7 +433,8 @@ int replay_revisions(struct rev_info *revs,
 
 		last_commit = pick_regular_commit(revs->repo, commit, replayed_commits,
 						  mode == REPLAY_MODE_REVERT ? last_commit : onto,
-						  &merge_opt, &result, mode, opts->empty);
+						  &merge_opt, &result, mode, opts->empty,
+						  opts->sign_commit);
 		if (!last_commit)
 			break;
 
diff --git a/replay.h b/replay.h
index faf95c7459..c715504d78 100644
--- a/replay.h
+++ b/replay.h
@@ -57,6 +57,12 @@ struct replay_revisions_options {
 	 */
 	int contained;
 
+	/*
+	 * Key used to sign newly-created commits. An empty string requests the
+	 * default configured signing key, and NULL disables signing.
+	 */
+	const char *sign_commit;
+
 	/*
 	 * Controls what to do when a replayed commit becomes empty.
 	 * Defaults to REPLAY_EMPTY_COMMIT_DROP.
-- 
2.55.0