But in `git checkout --patch`

But in `git checkout --patch`

[Benjamin Quorning]

I'm not entirely sure how you like your bug reports, so I'll just the
best I can :-)

$ git --version
git version 2.2.0

$ uname -a
Darwin buzz.local 13.4.0 Darwin Kernel Version 13.4.0: Sun Aug 17
19:50:11 PDT 2014; root:xnu-2422.115.4~1/RELEASE_X86_64 x86_64

Reproduction steps:

1. A repository with a changed file, but no staged changes.
2. Execute `git checkout --patch`
3. When asked, press `e` to edit a chunk (opens an external editor in my case)
4. With the editor still open, click ctrl-C in the terminal.
5. The diff that was being edited, and the command prompt ("discard
this hunk from worktree" etc) is printed to the screen, over and over
again.
6. I have to grep and kill this process: /usr/bin/perl
/usr/local/Cellar/git/2.2.0/libexec/git-core/git-add--interactive
--patch=checkout --

--
Benjamin Quorning

[PATCH] add--interactive: leave main loop on read error

[Jeff King]

On Mon, Dec 15, 2014 at 03:41:45PM +0100, Benjamin Quorning wrote:

> Reproduction steps:
> 
> 1. A repository with a changed file, but no staged changes.
> 2. Execute `git checkout --patch`
> 3. When asked, press `e` to edit a chunk (opens an external editor in my case)
> 4. With the editor still open, click ctrl-C in the terminal.
> 5. The diff that was being edited, and the command prompt ("discard
> this hunk from worktree" etc) is printed to the screen, over and over
> again.
> 6. I have to grep and kill this process: /usr/bin/perl
> /usr/local/Cellar/git/2.2.0/libexec/git-core/git-add--interactive
> --patch=checkout --

Thanks, I could reproduce this pretty easily with:

  GIT_EDITOR='f() { sleep 60; }; f' git checkout -p

(and then hit 'e', and ^C). Explanation and fix are below.

-- >8 --
The main hunk loop for add--interactive will loop if it does
not get a known input. This is a good thing if the user
typed some invalid input. However, if we have an
uncorrectable read error, we'll end up looping infinitely.
We can fix this by noticing read errors (i.e., <STDIN>
returns undef) and breaking out of the loop.

One easy way to trigger this is if you have an editor that
does not take over the terminal (e.g., one that spawns a
window in an existing process and waits), start the editor
with the hunk-edit command, and hit ^C to send SIGINT. The
editor process dies due to SIGINT, but the perl
add--interactive process does not (perl suspends SIGINT for
the duration of our system() call).

We return to the main loop, but further reads from stdin
don't work. The SIGINT _also_ killed our parent git process,
which orphans our process group, meaning that further reads
from the terminal will always fail. We loop infinitely,
getting EIO on each read.

Note that there are several other spots where we read from
stdin, too. However, in each of those cases, we do something
sane when the read returns undef (breaking out of the loop,
taking the input as "no", etc). They don't need similar
treatment.

Signed-off-by: Jeff King <peff@peff.net>
---
 git-add--interactive.perl | 1 +
 1 file changed, 1 insertion(+)

diff --git a/git-add--interactive.perl b/git-add--interactive.perl
index 1fadd69..c725674 100755
--- a/git-add--interactive.perl
+++ b/git-add--interactive.perl
@@ -1356,6 +1356,7 @@ sub patch_update_file {
 		  $patch_mode_flavour{TARGET},
 		  " [y,n,q,a,d,/$other,?]? ";
 		my $line = prompt_single_character;
+		last unless defined $line;
 		if ($line) {
 			if ($line =~ /^y/i) {
 				$hunk[$ix]{USE} = 1;
-- 
2.2.0.465.ge0d36f1.dirty

Re: [PATCH] add--interactive: leave main loop on read error

[Junio C Hamano]

Jeff King <peff@peff.net> writes:

> On Mon, Dec 15, 2014 at 03:41:45PM +0100, Benjamin Quorning wrote:
>
>> Reproduction steps:
>> 
>> 1. A repository with a changed file, but no staged changes.
>> 2. Execute `git checkout --patch`
>> 3. When asked, press `e` to edit a chunk (opens an external editor in my case)
>> 4. With the editor still open, click ctrl-C in the terminal.
>> 5. The diff that was being edited, and the command prompt ("discard
>> this hunk from worktree" etc) is printed to the screen, over and over
>> again.
>> 6. I have to grep and kill this process: /usr/bin/perl
>> /usr/local/Cellar/git/2.2.0/libexec/git-core/git-add--interactive
>> --patch=checkout --
>
> Thanks, I could reproduce this pretty easily with:
>
>   GIT_EDITOR='f() { sleep 60; }; f' git checkout -p
>
> (and then hit 'e', and ^C). Explanation and fix are below.
>
> -- >8 --
> The main hunk loop for add--interactive will loop if it does
> not get a known input. This is a good thing if the user
> typed some invalid input. However, if we have an
> uncorrectable read error, we'll end up looping infinitely.
> We can fix this by noticing read errors (i.e., <STDIN>
> returns undef) and breaking out of the loop.
>
> One easy way to trigger this is if you have an editor that
> does not take over the terminal (e.g., one that spawns a
> window in an existing process and waits), start the editor
> with the hunk-edit command, and hit ^C to send SIGINT. The
> editor process dies due to SIGINT, but the perl
> add--interactive process does not (perl suspends SIGINT for
> the duration of our system() call).
>
> We return to the main loop, but further reads from stdin
> don't work. The SIGINT _also_ killed our parent git process,
> which orphans our process group, meaning that further reads
> from the terminal will always fail. We loop infinitely,
> getting EIO on each read.
>
> Note that there are several other spots where we read from
> stdin, too. However, in each of those cases, we do something
> sane when the read returns undef (breaking out of the loop,
> taking the input as "no", etc). They don't need similar
> treatment.
>
> Signed-off-by: Jeff King <peff@peff.net>
> ---

Thanks.

>  git-add--interactive.perl | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/git-add--interactive.perl b/git-add--interactive.perl
> index 1fadd69..c725674 100755
> --- a/git-add--interactive.perl
> +++ b/git-add--interactive.perl
> @@ -1356,6 +1356,7 @@ sub patch_update_file {
>  		  $patch_mode_flavour{TARGET},
>  		  " [y,n,q,a,d,/$other,?]? ";
>  		my $line = prompt_single_character;
> +		last unless defined $line;
>  		if ($line) {
>  			if ($line =~ /^y/i) {
>  				$hunk[$ix]{USE} = 1;