log: fix indentation for --graph --show-signature

The git log --graph --show-signature command incorrectly indents the gpg
information about signed commits and merged signed tags. It does not
follow the level of indentation of the current commit.

Example of garbled output:
$ git log --show-signature --graph
*   commit 258e0a237cb69aaa587b0a4fb528bb0316b1b776
|\  gpg: Signature made Mon, Jun 30, 2014 13:22:33 EDT using RSA key ID DA08
gpg: Good signature from "Jason Pyeron <jpye...@pdinc.us>"
Merge: 727c355 1ca13ed
| | Author: Jason Pyeron <jpye...@pdinc.us>
| | Date:   Mon Jun 30 13:22:29 2014 -0400
| |
| |     Merge of 1ca13ed2271d60ba9 branch - rebranding
| |
| * commit 1ca13ed2271d60ba93d40bcc8db17ced8545f172
| | gpg: Signature made Mon, Jun 23, 2014  9:45:47 EDT using RSA key ID DD37
gpg: Good signature from "Stephen Robert Guglielmo <s...@guglielmo.us>"
gpg:                 aka "Stephen Robert Guglielmo <srguglie...@gmail.com>"
Author: Stephen R Guglielmo <s...@guglielmo.us>
| | Date:   Mon Jun 23 09:45:27 2014 -0400
| |
| |     Minor URL updates

In log-tree.c modify show_sig_lines() function to call graph_show_oneline()
after each line of gpg information it has printed in order to preserve
the level of indentation for the next output line.

Reported-by: Jason Pyeron <jpyeron@pdinc.us>
Signed-off-by: Zoltan Klinger <zoltan.klinger@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

log-tree.c

@@ -365,6 +365,7 @@ static void show_sig_lines(struct rev_info *opt, int status, const char *bol)
 		eol = strchrnul(bol, '\n');
 		printf("%s%.*s%s%s", color, (int)(eol - bol), bol, reset,
 		       *eol ? "\n" : "");
+		graph_show_oneline(opt->graph);
 		bol = (*eol) ? (eol + 1) : eol;
 	}
 }

t/t4202-log.sh

@@ -3,6 +3,7 @@
 test_description='git log'
 
 . ./test-lib.sh
+. "$TEST_DIRECTORY/lib-gpg.sh"
 
 test_expect_success setup '
 
@@ -841,4 +842,34 @@ test_expect_success 'dotdot is a parent directory' '
 	test_cmp expect actual
 '
 
+test_expect_success GPG 'log --graph --show-signature' '
+	test_when_finished "git reset --hard && git checkout master" &&
+	git checkout -b signed master &&
+	echo foo >foo &&
+	git add foo &&
+	git commit -S -m signed_commit &&
+	git log --graph --show-signature -n1 signed >actual &&
+	grep "^| gpg: Signature made" actual &&
+	grep "^| gpg: Good signature" actual
+'
+
+test_expect_success GPG 'log --graph --show-signature for merged tag' '
+	test_when_finished "git reset --hard && git checkout master" &&
+	git checkout -b plain master &&
+	echo aaa >bar &&
+	git add bar &&
+	git commit -m bar_commit &&
+	git checkout -b tagged master &&
+	echo bbb >baz &&
+	git add baz &&
+	git commit -m baz_commit &&
+	git tag -s -m signed_tag_msg signed_tag &&
+	git checkout plain &&
+	git merge --no-ff -m msg signed_tag &&
+	git log --graph --show-signature -n1 plain >actual &&
+	grep "^|\\\  merged tag" actual &&
+	grep "^| | gpg: Signature made" actual &&
+	grep "^| | gpg: Good signature" actual
+'
+
 test_done