[PATCH v6 15/45] builtin-am: reject patches when there's a session in progress

[Paul Tan <pyokagan@gmail.com>]

Since d1c5f2a (Add git-am, applymbox replacement., 2005-10-07), git-am
would error out if the user gave it mbox(s) on the command-line, but
there was a session in progress.

Since c95b138 (Fix git-am safety checks, 2006-09-15), git-am would
detect if the user attempted to feed it a mbox via stdin, by checking if
stdin is not a tty and there is no resume command given.

Re-implement the above two safety checks.

Signed-off-by: Paul Tan <pyokagan@gmail.com>
---
 builtin/am.c | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/builtin/am.c b/builtin/am.c
index 8a054ee..fa522f5 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -1147,6 +1147,21 @@ int cmd_am(int argc, const char **argv, const char *prefix)
 		die(_("failed to read the index"));
 
 	if (am_in_progress(&state)) {
+		/*
+		 * Catch user error to feed us patches when there is a session
+		 * in progress:
+		 *
+		 * 1. mbox path(s) are provided on the command-line.
+		 * 2. stdin is not a tty: the user is trying to feed us a patch
+		 *    from standard input. This is somewhat unreliable -- stdin
+		 *    could be /dev/null for example and the caller did not
+		 *    intend to feed us a patch but wanted to continue
+		 *    unattended.
+		 */
+		if (argc || (resume == RESUME_FALSE && !isatty(0)))
+			die(_("previous rebase directory %s still exists but mbox given."),
+				state.dir);
+
 		if (resume == RESUME_FALSE)
 			resume = RESUME_APPLY;
 
-- 
2.5.0.rc2.110.gb39b692