rebase -i: fix misleading error message after 'exec no-such' instruction

From: Johannes Sixt <[email protected]>

When the todo sheet of interactive rebase instructs to run a non-existing command, the operation stops with the following error:

Execution failed: no-such
You can fix the problem, and then run

          git rebase --continue

fatal: 'rebase' appears to be a git command, but we were not able to execute it. Maybe git-rebase is broken?

The reason is that the shell that attempted to run the command exits with code 127. rebase--interactive just forwards this code to the caller (the git wrapper). But our smart run-command infrastructure detects this special exit code and turns it into ENOENT, which in turn is interpreted by the git wrapper as if the external command that it just executed did not exist. This is finally translated to the misleading last two lines in error message cited above.

Fix it by translating the error code before it is forwarded.

---
An alternative fix would be to just ignore the shell's status code. I decided that it is worth keeping it: better safe than sorry.

BTW, the problem existed since day 1 of the 'exec' feature.

 git-rebase--interactive.sh    |  4 ++++
 t/t3404-rebase-interactive.sh | 11 +++++++++++
 2 files changed, 15 insertions(+)

index a09e842..56707d7 100644
@@ -544,6 +544,10 @@ do_next () {
 			warn
 			warn "	git rebase --continue"
 			warn
+			if test $status -eq 127		# command not found
+			then
+				status=1
+			fi
 			exit "$status"
 		elif test "$dirty" = t
 		then

index 7304b66..7a71760 100755
@@ -118,6 +118,17 @@ test_expect_success 'rebase -i with the exec command checks tree cleanness' '
 	git rebase --continue
 '
 
+test_expect_success 'rebase -i with exec of inexistent command' '
+	git checkout master &&
+	test_when_finished "git rebase --abort" &&
+	(
+	FAKE_LINES="exec_this-command-does-not-exist 1" &&
+	export FAKE_LINES &&
+	test_must_fail git rebase -i HEAD^ >actual 2>&1
+	) &&
+	! grep "Maybe git-rebase is broken" actual
+'
+
 test_expect_success 'no changes are a nop' '
 	git checkout branch2 &&
 	git rebase -i F &&

1.7.12.1720.gb55457a.dirty

That's a funny one ;-)
Will queue. Thanks.

While you're there, maybe you want to turn the first line into

Execution failed: no-such (command not found)

In any case, the patch sounds good, thanks.

Matthieu Moy
http://www-verimag.imag.fr/~moy/

Am 9/18/2012 13:20, schrieb Matthieu Moy:

No, I don't want to: Neither do we have errno here, nor can we be specific enough because the whole shell script the user gave after 'exec' is repeated here.

I would rather remove the line so that it does not distract from the more specific error message that the shell gave. On top of that, the command is already dumped before it is executed; we don't need to repeat it.

-- Hannes

Not sure what you mean: remove the line in case $status = 127, or remove it anyway.

If you mean only when $status = 127, then that is indeed a good idea, as the full error message looks like

Executing: nosuchcommand
zsh:1: command not found: nosuchcommand
Execution failed: nosuchcommand
You can fix the problem, and then run [...]

So, yes, the shell's error message is enough and more precise than we could do in git rebase.

If you mean remove it in any case, I disagree: repeating the command is usually not very useful, but may help when the command itself produced a lot of output (e.g. "exec make test" oftens fills-in your terminal's buffer). And the information that the command fails can be important if the command failed silently, e.g. with "exec false":

Executing: false
Execution failed: false
You can fix the problem, and then run [...]

Matthieu Moy
http://www-verimag.imag.fr/~moy/