[RFC PATCH] sequencer: fix quoting in write_author_script

[Phillip Wood <phillip.wood@talktalk.net>]

From: Phillip Wood <phillip.wood@dunelm.org.uk>

Single quotes should be escaped as \' not \\'. Note that this only
affects authors that contain a single quote and then only external
scripts that read the author script and users whose git is upgraded from
the shell version of rebase -i while rebase was stopped. This is because
the parsing in read_env_script() expected the broken version and for
some reason sq_dequote() called by read_author_ident() seems to handle
the broken quoting correctly.

Ideally write_author_script() would be rewritten to use
split_ident_line() and sq_quote_buf() but this commit just fixes the
immediate bug.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
---

This is untested, unfortuantely I don't have really have time to write a test or
follow this up at the moment, if someone else want to run with it then please
do.

sequencer.c | 18 +++++++++++++-----
 1 file changed, 13 insertions(+), 5 deletions(-)

diff --git a/sequencer.c b/sequencer.c
index 5354d4d51e..0b78d1f100 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -638,21 +638,21 @@ static int write_author_script(const char *message)
 		else if (*message != '\'')
 			strbuf_addch(&buf, *(message++));
 		else
-			strbuf_addf(&buf, "'\\\\%c'", *(message++));
+			strbuf_addf(&buf, "'\\%c'", *(message++));
 	strbuf_addstr(&buf, "'\nGIT_AUTHOR_EMAIL='");
 	while (*message && *message != '\n' && *message != '\r')
 		if (skip_prefix(message, "> ", &message))
 			break;
 		else if (*message != '\'')
 			strbuf_addch(&buf, *(message++));
 		else
-			strbuf_addf(&buf, "'\\\\%c'", *(message++));
+			strbuf_addf(&buf, "'\\%c'", *(message++));
 	strbuf_addstr(&buf, "'\nGIT_AUTHOR_DATE='@");
 	while (*message && *message != '\n' && *message != '\r')
 		if (*message != '\'')
 			strbuf_addch(&buf, *(message++));
 		else
-			strbuf_addf(&buf, "'\\\\%c'", *(message++));
+			strbuf_addf(&buf, "'\\%c'", *(message++));
 	res = write_message(buf.buf, buf.len, rebase_path_author_script(), 1);
 	strbuf_release(&buf);
 	return res;
@@ -666,13 +666,21 @@ static int read_env_script(struct argv_array *env)
 {
 	struct strbuf script = STRBUF_INIT;
 	int i, count = 0;
-	char *p, *p2;
+	const char *p2;
+	char *p;
 
 	if (strbuf_read_file(&script, rebase_path_author_script(), 256) <= 0)
 		return -1;
 
 	for (p = script.buf; *p; p++)
-		if (skip_prefix(p, "'\\\\''", (const char **)&p2))
+		/*
+		 * write_author_script() used to escape "'" incorrectly as
+		 * "'\\\\''" rather than "'\\''" so we check for the correct
+		 * version the incorrect version in case git was upgraded while
+		 * rebase was stopped.
+		 */
+		if (skip_prefix(p, "'\\''", &p2) ||
+		    skip_prefix(p, "'\\\\''", &p2))
 			strbuf_splice(&script, p - script.buf, p2 - p, "'", 1);
 		else if (*p == '\'')
 			strbuf_splice(&script, p-- - script.buf, 1, "", 0);
-- 
2.18.0