But in `git checkout --patch`

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 --

Quoted 12 lines · Benjamin Quorning

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 <[email protected]>

---

 git-add--interactive.perl | 1 +
 1 file changed, 1 insertion(+)

git-add--interactive.perl +1 -0

index 1fadd69..c725674 100755
@@ -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;