commit-tree: add the commit.gpgsign option to sign all commits

If you want to GPG sign all your commits, you have to add the -S option
all the time. The commit.gpgsign config option allows to sign all
commits automatically.
Signed-off-by: NNicolas Vigier <boklm@mars-attacks.org>
Signed-off-by: NJunio C Hamano <gitster@pobox.com>

Documentation/config.txt

@@ -988,6 +988,14 @@ commit.cleanup::
 	have to remove the help lines that begin with `#` in the commit log
 	template yourself, if you do this).
 
+commit.gpgsign::
+
+	A boolean to specify whether all commits should be GPG signed.
+	Use of this option when doing operations such as rebase can
+	result in a large number of commits being signed. It may be
+	convenient to use an agent to avoid typing your GPG passphrase
+	several times.
+
 commit.status::
 	A boolean to enable/disable inclusion of status information in the
 	commit message template when using an editor to prepare the commit

builtin/commit-tree.c

@@ -12,6 +12,8 @@
 
 static const char commit_tree_usage[] = "git commit-tree [(-p <sha1>)...] [-S[<keyid>]] [-m <message>] [-F <file>] <sha1> <changelog";
 
+static const char *sign_commit;
+
 static void new_parent(struct commit *parent, struct commit_list **parents_p)
 {
 	unsigned char *sha1 = parent->object.sha1;
@@ -31,6 +33,10 @@ static int commit_tree_config(const char *var, const char *value, void *cb)
 	int status = git_gpg_config(var, value, NULL);
 	if (status)
 		return status;
+	if (!strcmp(var, "commit.gpgsign")) {
+		sign_commit = git_config_bool(var, value) ? "" : NULL;
+		return 0;
+	}
 	return git_default_config(var, value, cb);
 }
 
@@ -41,7 +47,6 @@ int cmd_commit_tree(int argc, const char **argv, const char *prefix)
 	unsigned char tree_sha1[20];
 	unsigned char commit_sha1[20];
 	struct strbuf buffer = STRBUF_INIT;
-	const char *sign_commit = NULL;
 
 	git_config(commit_tree_config, NULL);
 

builtin/commit.c

@@ -1406,6 +1406,10 @@ static int git_commit_config(const char *k, const char *v, void *cb)
 	}
 	if (!strcmp(k, "commit.cleanup"))
 		return git_config_string(&cleanup_arg, k, v);
+	if (!strcmp(k, "commit.gpgsign")) {
+		sign_commit = git_config_bool(k, v) ? "" : NULL;
+		return 0;
+	}
 
 	status = git_gpg_config(k, v, NULL);
 	if (status)

builtin/merge.c

@@ -604,6 +604,9 @@ static int git_merge_config(const char *k, const char *v, void *cb)
 	} else if (!strcmp(k, "merge.defaulttoupstream")) {
 		default_to_upstream = git_config_bool(k, v);
 		return 0;
+	} else if (!strcmp(k, "commit.gpgsign")) {
+		sign_commit = git_config_bool(k, v) ? "" : NULL;
+		return 0;
 	}
 
 	status = fmt_merge_msg_config(k, v, cb);