# Zulip-specific tools

This article documents several useful tools that can save you a lot of
time when working with Git on the Zulip project.

## Set up Git repo script

**Extremely useful**.  In the `tools` directory of
[zulip/zulip][github-zulip-zulip] you'll find a bash script
`setup-git-repo`. This script installs a pre-commit hook, which will
run each time you `git commit` to automatically run
[Zulip's linter suite](../testing/linters.md) on just the files that
the commit modifies (which is really fast!). The hook passes no matter
the result of the linter, but you should still pay attention to any
notices or warnings it displays.

It's simple to use. Make sure you're in the clone of zulip and run the following:

```
$ ./tools/setup-git-repo
```

The script doesn't produce any output if successful. To check that the hook has
been installed, print a directory listing for `.git/hooks` and you should see
something similar to:

```
$ ls -l .git/hooks
pre-commit -> ../../tools/pre-commit
```

## Configure continuous integration for your Zulip fork

You might also wish to [configure continuous integration for your fork][zulip-git-guide-ci].

## Reset to pull request

`tools/reset-to-pull-request` is a short-cut for [checking out a pull request
locally][zulip-git-guide-fetch-pr]. It works slightly differently from the method
described above in that it does not create a branch for the pull request
checkout.

**This tool checks for uncommitted changes, but it will move the
  current branch using `git reset --hard`.  Use with caution.**

First, make sure you are working in a branch you want to move (in this
example, we'll use the local `master` branch). Then run the script
with the ID number of the pull request as the first argument.

```
$ git checkout master
Switched to branch 'master'
Your branch is up-to-date with 'origin/master'.

$ ./tools/reset-to-pull-request 1900
+ request_id=1900
+ git fetch upstream pull/1900/head
remote: Counting objects: 159, done.
remote: Compressing objects: 100% (17/17), done.
remote: Total 159 (delta 94), reused 91 (delta 91), pack-reused 51
Receiving objects: 100% (159/159), 55.57 KiB | 0 bytes/s, done.
Resolving deltas: 100% (113/113), completed with 54 local objects.
From https://github.com/zulip/zulip
 * branch            refs/pull/1900/head -> FETCH_HEAD
+ git reset --hard FETCH_HEAD
HEAD is now at 2bcd1d8 troubleshooting tip about provisioning
```

## Fetch a pull request and rebase

`tools/fetch-rebase-pull-request` is a short-cut for [checking out a pull
request locally][zulip-git-guide-fetch-pr] in its own branch and then updating it with any
changes from upstream/master with `git rebase`.

Run the script with the ID number of the pull request as the first argument.

```
$ tools/fetch-rebase-pull-request 1913
+ request_id=1913
+ git fetch upstream pull/1913/head
remote: Counting objects: 4, done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 4 (delta 0), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (4/4), done.
From https://github.com/zulip/zulip
 * branch            refs/pull/1913/head -> FETCH_HEAD
+ git checkout upstream/master -b review-1913
Branch review-1913 set up to track remote branch master from upstream.
Switched to a new branch 'review-1913'
+ git reset --hard FETCH_HEAD
HEAD is now at 99aa2bf Add provision.py fails issue in common errors
+ git pull --rebase
Current branch review-1913 is up to date.
```

## Fetch a pull request without rebasing

`tools/fetch-pull-request` is a similar to `tools/fetch-rebase-pull-request`, but
it does not rebase the pull request against upstream/master, thereby getting
exactly the same repository state as the commit author had.

Run the script with the ID number of the pull request as the first argument.

```
$ tools/fetch-pull-request 5156
+ git diff-index --quiet HEAD
+ request_id=5156
+ remote=upstream
+ git fetch upstream pull/5156/head
From https://github.com/zulip/zulip
 * branch            refs/pull/5156/head -> FETCH_HEAD
+ git checkout -B review-original-5156
Switched to a new branch 'review-original-5156'
+ git reset --hard FETCH_HEAD
HEAD is now at 5a1e982 tools: Update clean-branches to clean review branches.
```

## Push to a pull request

`tools/push-to-pull-request` is primarily useful for maintainers who
are merging other users' commits into a Zulip repository.  After doing
`reset-to-pull-request` or `fetch-pull-request` and making some
changes, you can push a branch back to a pull request with e.g.
`tools/push-to-pull-request 1234`.  This is useful for a few things:

* Getting CI to run and enabling you to use the GitHub "Merge" buttons
  to merge a PR after you make some corrections to a PR, without
  waiting for an extra round trip with the PR author.
* For commits that aren't ready to merge yet, communicating clearly
  any changes you'd like to see happen that are easier for you to
  explain by just editing the code than in words.
* Saving a contributor from needing to duplicate any rebase work that
  you did as part of integrating parts of the PR.

You'll likely want to comment on the PR after doing so, to ensure that
the original contributor knows to pull your changes rather than
accidentally overwriting them with a force push when they make their
next batch of changes.

Note that in order to do this you need permission to do such a push,
which GitHub offers by default to users with write access to the
repository.  For multiple developers collaborating on a PR, you can
achieve this by granting other users permission to write to your fork.

## Delete unimportant branches

`tools/clean-branches` is a shell script that removes branches that are either:

1. Local branches that are ancestors of origin/master.
2. Branches in origin that are ancestors of origin/master and named like `$USER-*`.
3. Review branches created by `tools/fetch-rebase-pull-request` and `tools/fetch-pull-request`.

First, make sure you are working in branch `master`. Then run the script without any
arguments for default behavior. Since removing review branches can inadvertently remove any
feature branches whose names are like `review-*`, it is not done by default. To
use it, run `tools/clean-branches --reviews`.

```
$ tools/clean-branches --reviews
Deleting local branch review-original-5156 (was 5a1e982)
```

## Merge conflict on yarn.lock file

If there is a merge conflict on yarn.lock, yarn should be run to
regenerate the file. *Important* don't delete the yarn.lock file. Check out the
latest one from origin/master so that yarn knows the previous asset versions.

Run the following commands
```
git checkout origin/master -- yarn.lock
yarn install
git add yarn.lock
git rebase --continue
```

[github-zulip-zulip]: https://github.com/zulip/zulip/
[zulip-git-guide-fetch-pr]: ../git/collaborate.html#check-out-a-pull-request-locally
[zulip-git-guide-ci]: ../git/cloning.html#step-3-configure-continuous-integration-for-your-fork