Fix backport script on OS X

[nylen]

Issue reported by @bahiirwa:

$ bin/backport-wp-commit.sh -c 42832
Found git remote 'wp' for WordPress/wordpress-develop
Found git remote 'origin' for ClassicPress/ClassicPress
Updating repositories from GitHub: WordPress...
Updating repositories from GitHub: ClassicPress...
Searching for r42832 in WP git: wp/4.9
Searching for r42832 in WP git: wp/5.0
Searching for r42832 in WP git: wp/5.1
Searching for r42832 in WP git: wp/5.2
Searching for r42832 in WP git: wp/5.3
Searching for r42832 in WP git: wp/5.4
Searching for r42832 in WP git: wp/master

Found commit: 5f56921131 on wp/master branch

Backporting commit using git cherry-pick
Modifying commit message

git status before:
UU src/wp-admin/css/dashboard.css
UU src/wp-admin/includes/dashboard.php
UU src/wp-includes/capabilities.php
UU tests/phpunit/tests/user/capabilities.php

usage: grep [-abcDEFGHhIiJLlmnOoqRSsUVvwxZ] [-A num] [-B num] [-C[num]]
        [-e pattern] [-f file] [--binary-files=value] [--color=when]
        [--context[=num]] [--directories=action] [--label] [--line-buffered]
        [--null] [pattern] [file ...]
usage: grep [-abcDEFGHhIiJLlmnOoqRSsUVvwxZ] [-A num] [-B num] [-C[num]]
        [-e pattern] [-f file] [--binary-files=value] [--color=when]
        [--context[=num]] [--directories=action] [--label] [--line-buffered]
        [--null] [pattern] [file ...]

git status after:
UU src/wp-admin/css/dashboard.css
UU src/wp-admin/includes/dashboard.php
UU src/wp-includes/capabilities.php
UU tests/phpunit/tests/user/capabilities.php

+ git commit --no-edit --allow-empty --author=Felix Arntz <flixos90@git.wordpress.org>
> error: Committing is not possible because you have unmerged files.
> hint: Fix them up in the work tree, and then use 'git add/rm <file>'
> hint: as appropriate to mark resolution and make a commit.
> fatal: Exiting because of an unresolved conflict.
> U     src/wp-admin/css/dashboard.css
> U     src/wp-admin/includes/dashboard.php
> U     src/wp-includes/capabilities.php
> U     tests/phpunit/tests/user/capabilities.php

OS X grep supports -E but not -P: https://ss64.com/osx/grep.html

The same issue exists in the Gruntfile for grunt precommit:git-conflicts so this PR should fix that too.

[bahiirwa]

This now works as expected.

This is my latest log from console on backport.

laurencebahiirwa@Laurences-iMac classicpress % git co -t origin/fix/backport-script-osx
Branch 'fix/backport-script-osx' set up to track remote branch 'fix/backport-script-osx' from 'origin'.
Switched to a new branch 'fix/backport-script-osx'
laurencebahiirwa@Laurences-iMac classicpress % bin/backport-wp-commit.sh -c 42832
Found git remote 'wp' for WordPress/wordpress-develop
Found git remote 'origin' for ClassicPress/ClassicPress
Updating repositories from GitHub: WordPress...
Updating repositories from GitHub: ClassicPress...
Searching for r42832 in WP git: wp/4.9
Searching for r42832 in WP git: wp/5.0
Searching for r42832 in WP git: wp/5.1
Searching for r42832 in WP git: wp/5.2
Searching for r42832 in WP git: wp/5.3
Searching for r42832 in WP git: wp/5.4
Searching for r42832 in WP git: wp/master

Found commit: 5f56921131 on wp/master branch

Backporting commit using git cherry-pick
Modifying commit message

git status before:
UU src/wp-admin/css/dashboard.css
UU src/wp-admin/includes/dashboard.php
UU src/wp-includes/capabilities.php
UU tests/phpunit/tests/user/capabilities.php


git status after:
M  src/wp-admin/css/dashboard.css
M  src/wp-admin/includes/dashboard.php
M  src/wp-includes/capabilities.php
M  tests/phpunit/tests/user/capabilities.php


=======
WARNING: Conflict detected!
Fix and commit the files that contain <<<< or >>>> conflict markers:
    - src/wp-admin/css/dashboard.css
    - src/wp-admin/includes/dashboard.php
    - src/wp-includes/capabilities.php
    - tests/phpunit/tests/user/capabilities.php
=======

If you're not sure how to do this, just push your changes to GitHub
and we can take care of it!

1 commit was added to your current branch.
laurencebahiirwa@Laurences-iMac classicpress % 

With the changes being backported and commited with conflicts as should be.

[mattyrob]

I'm on MacOS and until I stumbled across this ticket I hadn't really even noticed the error message.

With this patch applied I can push a changes without having to commit the files with conflicts first - saves a step for me and makes the preferred process easier for patch review.

[nylen]

I think this explains most of the malformed PRs that have been coming through. Thanks both of you for taking a look and confirming this now works as expected, I'll merge it now.

[ClassyBot]

This pull request has been mentioned on ClassicPress Forums. There might be relevant details there:

https://forums.classicpress.net/t/classicpress-1-2-0-release-notes/2516/1