GIT HOOKS: manage custom installer paths during development.

[molleweide]

I am looking into git hooks to automate the process of setting up custom config paths
when developing and then resetting the paths when pushing back to upstream.

Use-case: doom-nvim

The default of doom-nvim is for user to install to ~/.config/nvim but since I/we
are using Cheovim I do believe that most of us are using a custom installer location.
Therefor, it would be nice to setup post-checkout and pre-push hooks that take care
of modifying the doom root path so that one doesn't need to always update these paths
manually when switching between local dev/personal branch and a, (in my case), temporary
fetch of upstream development in order to apply patch/rebase/cherry-pick commits etc.

This could then be a recommendation in contribution docs to add these two hooks should
one like to.

Note

Personally I have never used hooks before so I am posting my research here. ;)

resources

Below are interesting links that I have found.

resources: post-checkout

https://stackoverflow.com/questions/1011557/is-there-a-way-to-trigger-a-hook-after-a-new-branch-has-been-checked-out-in-git
https://stackoverflow.com/questions/2141492/git-clone-and-post-checkout-hook
https://gist.github.com/lyrixx/5867424
https://gist.github.com/stefansundin/82051ad2c8565999b914

resources: pre-push

https://gist.github.com/mosra/19abea23cdf6b82ce891c9410612e7e1
https://gist.github.com/ashtanko/5f5221262af66d79c775d68d814f4e22

Example 1: post-checkout

do stuff when checking out branch locally

example source

Example:

1. Create the hook (script):

touch .git/hooks/post-checkout
chmod u+x .git/hooks/post-checkout

2. Hook sample content:

#!/bin/bash                                                                      

set -e                                                                           

printf '\npost-checkout hook\n\n'                                                

prevHEAD=$1                                                                      
newHEAD=$2                                                                       
checkoutType=$3                                                                  

[[ $checkoutType == 1 ]] && checkoutType='branch' ||                             
                            checkoutType='file' ;                                

echo 'Checkout type: '$checkoutType                                              
echo '    prev HEAD: '`git name-rev --name-only $prevHEAD`                       
echo '     new HEAD: '`git name-rev --name-only $newHEAD`

3. Result

#> git checkout -
Switched to branch 'molldev'

post-checkout hook

Checkout type: branch
    prev HEAD: pr_prep_branch
    new HEAD: molldev

Example 2: pre-push

taken from .git/hooks/pre-push.sample

#!/bin/sh

# An example hook script to verify what is about to be pushed.  Called by "git
# push" after it has checked the remote status, but before anything has been
# pushed.  If this script exits with a non-zero status nothing will be pushed.
#
# This hook is called with the following parameters:
#
# $1 -- Name of the remote to which the push is being done
# $2 -- URL to which the push is being done
#
# If pushing without using a named remote those arguments will be equal.
#
# Information about the commits which are being pushed is supplied as lines to
# the standard input in the form:
#
#   <local ref> <local oid> <remote ref> <remote oid>
#
# This sample shows how to prevent push of commits where the log message starts
# with "WIP" (work in progress).

remote="$1"
url="$2"

zero=$(git hash-object --stdin </dev/null | tr '[0-9a-f]' '0')

while read local_ref local_oid remote_ref remote_oid
do
	if test "$local_oid" = "$zero"
	then
		# Handle delete
		:
	else
		if test "$remote_oid" = "$zero"
		then
			# New branch, examine all commits
			range="$local_oid"
		else
			# Update to existing branch, examine new commits
			range="$remote_oid..$local_oid"
		fi

		# Check for WIP commit
		commit=$(git rev-list -n 1 --grep '^WIP' "$range")
		if test -n "$commit"
		then
			echo >&2 "Found WIP commit in $local_ref, not pushing"
			exit 1
		fi
	fi
done

exit 0