threads / discuss / 24843

Why does git-mergetool use /dev/tty?

Subject: Why does git-mergetool use /dev/tty?

## tl;dr

5 messages between Aug 24, 2010 and Aug 24, 2010.

replies: 4people: 3as markdown or json

Brian Gernhardt· Aug 24, 2010, 01:49 UTC · lore

git-mergetool.sh, lines 298-302:

Show 5 quoted lines

>     if test $last_status -ne 0; then
>         prompt_after_failed_merge < /dev/tty || exit 1
>     fi
>     printf "\n"
>     merge_file "$i" < /dev/tty > /dev/tty

Why does git-mergetool ignore the provided STDIN and STDOUT when not given a path to merge?

This wasn't apparent until bb0a484: "mergetool: Skip autoresolved paths" added a test that doesn't provide a file to merge on the command line.

~~ Brian Gernhardt

Jonathan Nieder· Aug 24, 2010, 01:53 UTC · re: Brian Gernhardt · lore

Re: Why does git-mergetool use /dev/tty?

Brian Gernhardt wrote:

> Why does git-mergetool ignore the provided STDIN and STDOUT when not given a path to merge?

See af314714 (mergetool: Remove explicit references to /dev/tty, 2010-08-20) in pu.

Hope that helps, Jonathan

Brian Gernhardt· Aug 24, 2010, 01:58 UTC · re: Jonathan Nieder · lore

Re: Why does git-mergetool use /dev/tty?

On Aug 23, 2010, at 9:53 PM, Jonathan Nieder wrote:

Show 8 quoted lines

> Brian Gernhardt wrote:
> 
>> Why does git-mergetool ignore the provided STDIN and STDOUT when not given a path to merge?
> 
> See af314714 (mergetool: Remove explicit references to /dev/tty,
> 2010-08-20) in pu.
> 
> Hope that helps,

It does really help, actually.  One thing removed from my TODO.

~~ Brian

Charles Bailey· Aug 24, 2010, 06:43 UTC · re: Brian Gernhardt · lore

Re: Why does git-mergetool use /dev/tty?

On Mon, Aug 23, 2010 at 09:49:57PM -0400, Brian Gernhardt wrote:

Show 8 quoted lines

> git-mergetool.sh, lines 298-302:
> >     if test $last_status -ne 0; then
> >         prompt_after_failed_merge < /dev/tty || exit 1
> >     fi
> >     printf "\n"
> >     merge_file "$i" < /dev/tty > /dev/tty
> 
> Why does git-mergetool ignore the provided STDIN and STDOUT when not given a path to merge?

It doesn't deliberately ignore them, it merely loses them because what you've quoted is in the middle of a redirect, you snipped:

    files_to_merge |
    while IFS= read i
    do

mergetool is designed to be an interactive tool and didn't originally have any tests so this was a reasonable (if ugly) way to restore access to the user for the merge_file function.

This is also why all the previous test provided an explict list of files to merge, because this was the only testable way to invoke mergetool.

There's a proposed patch to save and restore the original stdin instead of assuming that there is a tty in pu: af314714.

If the current behaviour is causing an issue for you then testing this fix would be appreciated.

Thanks,

Charles.

Brian Gernhardt· Aug 24, 2010, 07:04 UTC · re: Charles Bailey · lore

Re: Why does git-mergetool use /dev/tty?

On Aug 24, 2010, at 2:43 AM, Charles Bailey wrote:

Show 5 quoted lines

> There's a proposed patch to save and restore the original stdin
> instead of assuming that there is a tty in pu: af314714.
> 
> If the current behaviour is causing an issue for you then testing this
> fix would be appreciated.

The issue was spurious output during tests, which is fixed by af314714.

Thanks for the explanation though, I had missed that it was part of a pipeline.

~~ Brian