Re: [PATCH 1/3] rebase: guard against missing files in read_basic_state()

Martin von Zweigbergk [off-list ref] writes:

On Thu, Jun 13, 2013 at 3:29 PM, Junio C Hamano [off-list ref] wrote:

quoted

Ramkumar Ramachandra [off-list ref] writes:

A more troublesome is that nobody seems to check the return value of
this function.  If head-name, onto or orig-head is missing, is that
an error condition that should make the callers of read_basic_state
stop and refuse to proceed?

Since we unconditionally write those three (and 'quiet'), it seems
reasonable to require all of them to be there when continuing, so I
think you're right that we should fail fast.

quoted

The way the && cascade is used seems to indicate that, but up to the
point where it sents $verbose. If and only if head-name, onto, orig-head
and quiet can be read in state-dir, verbose in state-dir is checked
and only then $verbose is set.

Martin, this seems to be from your series around early Feburary
2011.  Do you recall why these checks are cascaded this way?
I do not offhand think of a good reason.

Neither do I. I think the cascading after 'quiet' is just a mistake on
my part. The consequences are probably close to none, since if one of
earlier commands fail, the other files will probably not be there
either. (Not defending it; I'm happy if it gets fixed, e.g. by making
it fail fast.)

I think this is probably the right thing to do, if we want to honor
the original intention of the earlier part of && cascade.  Everything
before this new "|| die" reads from a file that should always exist
(e.g. even when not asked to be quiet, that state is not signaled by
the lack of $state_dir/quiet, but by having an empty string in it),
while everything after check optional state variable files (e.g. if
$state_dir/verbose does not exist, it is not an error, but signals
that the user did not ask us to be verbose).

Note that applying this patch _could_ uncover latent bug that was
masked by the lack of "die" here (maybe later codepath may depended
on not having orig_head at all and the only observable effect was
that in such a case, both quiet and verbose were silently ignored,
because the control did not reach the GIT_QUIET=... and verbose=t
assignments.

 git-rebase.sh | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/git-rebase.sh b/git-rebase.sh
index d0c11a9..90506ba 100755
--- a/git-rebase.sh
+++ b/git-rebase.sh

@@ -95,7 +95,9 @@ read_basic_state () {
 	else
 		orig_head=$(cat "$state_dir"/head)
 	fi &&
-	GIT_QUIET=$(cat "$state_dir"/quiet) &&
+	GIT_QUIET=$(cat "$state_dir"/quiet) ||
+	die "failed to read basic rebase state from $state_dir"
+
 	test -f "$state_dir"/verbose && verbose=t
 	test -f "$state_dir"/strategy && strategy="$(cat "$state_dir"/strategy)"
 	test -f "$state_dir"/strategy_opts &&