[PATCH 16/22] sequencer: prepare for rebase -i's GPG settings

[Johannes Schindelin <johannes.schindelin@xxxxxx>]

The rebase command sports a `--gpg-sign` option that is heeded by the
interactive rebase.

This patch teaches the sequencer that trick, as part of the bigger
effort to make the sequencer the work horse of the interactive rebase.

Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
 sequencer.c | 48 +++++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 43 insertions(+), 5 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 4204cc8..e094ac2 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -15,6 +15,7 @@
 #include "merge-recursive.h"
 #include "refs.h"
 #include "argv-array.h"
+#include "quote.h"
 
 #define GIT_REFLOG_ACTION "GIT_REFLOG_ACTION"
 
@@ -33,6 +34,11 @@ static GIT_PATH_FUNC(git_path_head_file, "sequencer/head")
  * being rebased.
  */
 static GIT_PATH_FUNC(rebase_path_author_script, "rebase-merge/author-script")
+/*
+ * The following files are written by git-rebase just after parsing the
+ * command-line (and are only consumed, not modified, by the sequencer).
+ */
+static GIT_PATH_FUNC(rebase_path_gpg_sign_opt, "rebase-merge/gpg_sign_opt")
 
 /* We will introduce the 'interactive rebase' mode later */
 #define IS_REBASE_I() 0
@@ -129,6 +135,16 @@ static int has_conforming_footer(struct strbuf *sb, struct strbuf *sob,
 	return 1;
 }
 
+static const char *gpg_sign_opt_quoted(struct replay_opts *opts)
+{
+	static struct strbuf buf = STRBUF_INIT;
+
+	strbuf_reset(&buf);
+	if (opts->gpg_sign)
+		sq_quotef(&buf, "-S%s", opts->gpg_sign);
+	return buf.buf;
+}
+
 void *sequencer_entrust(struct replay_opts *opts, void *set_me_free_after_use)
 {
 	ALLOC_GROW(opts->owned, opts->owned_nr + 1, opts->owned_alloc);
@@ -471,17 +487,20 @@ int sequencer_commit(const char *defmsg, struct replay_opts *opts,
 
 	if (IS_REBASE_I()) {
 		env = read_author_script();
-		if (!env)
+		if (!env) {
+			const char *gpg_opt = gpg_sign_opt_quoted(opts);
+
 			return error("You have staged changes in your working "
 				"tree. If these changes are meant to be\n"
 				"squashed into the previous commit, run:\n\n"
-				"  git commit --amend $gpg_sign_opt_quoted\n\n"
+				"  git commit --amend %s\n\n"
 				"If they are meant to go into a new commit, "
 				"run:\n\n"
-				"  git commit $gpg_sign_opt_quoted\n\n"
+				"  git commit %s\n\n"
 				"In both case, once you're done, continue "
 				"with:\n\n"
-				"  git rebase --continue\n");
+				"  git rebase --continue\n", gpg_opt, gpg_opt);
+		}
 	}
 
 	argv_array_init(&array);
@@ -955,8 +974,27 @@ static int populate_opts_cb(const char *key, const char *value, void *data)
 
 static int read_populate_opts(struct replay_opts *opts)
 {
-	if (IS_REBASE_I())
+	if (IS_REBASE_I()) {
+		struct strbuf buf = STRBUF_INIT;
+
+		if (read_oneliner(&buf, rebase_path_gpg_sign_opt(), 1)) {
+			if (buf.len && buf.buf[buf.len - 1] == '\n') {
+				if (--buf.len &&
+				    buf.buf[buf.len - 1] == '\r')
+					buf.len--;
+				buf.buf[buf.len] = '\0';
+			}
+
+			if (!starts_with(buf.buf, "-S"))
+				strbuf_reset(&buf);
+			else {
+				opts->gpg_sign = buf.buf + 2;
+				strbuf_detach(&buf, NULL);
+			}
+		}
+
 		return 0;
+	}
 
 	if (!file_exists(git_path_opts_file()))
 		return 0;
-- 
2.10.0.rc1.114.g2bd6b38