what are GitHub 'refs/pull/*' refspecs and how to get full copy of GitHub repo [git] [github]

script.sh

#!/usr/bin/env bash

# we are going to fetch all refs (including 'refs/pull/*') from Git remote
#   'repo-to-fetch', which points to public GitHub repo defined by URL
#   '${repoURL}' where the GitHub user account '${userName}' has write access
# for more details on GitHub 'refs/pull/*' refspecs see [1]

userName=mxxxxxx
userEmail=mxxxxxx@xxxxx.xxx
repoURL=https://github.com/txxxx-xx/gxx-xxxx.git

# create, init, and configure git repo
mkdir bare-repo
cd bare-repo

git init --bare
git config  user.email ${userEmail}
git config  user.name ${userName}
git config  credential.username ${userName}

# set up 'repo-to-fetch' remote, you NEED TO CREATE new GitHub repo
#   preliminarily
git remote add --mirror=fetch repo-to-fetch ${repoURL}

# see default set of 'refspec' for the created remote (for 'git fetch'
#   command)
git config --get-all remote.repo-to-fetch.fetch # output: '+refs/*:refs/*'

# see existing branches and tags before fetch
git branch -avv   | wc -l # output: 0
git tag -l        | wc -l # output: 0
find refs -type f | wc -l # output: 0
tree refs # output:
#> refs
#> ├── heads
#> └── tags
#>
#> 2 directories, 0 files

# fetch updates from 'repo-to-fetch' remote
git remote update 2>&1 | grep "^ \*" > log

# examine log
cat log | wc -l                     # output: '      20'
cat log | grep "new branch" | wc -l # output: '       3'
cat log | grep "new ref" | wc -l    # output: '      11'
cat log | grep "new tag" | wc -l    # output: '       6'

# see existing branches and tags after fetch (with help of git command)
git branch -avv   | wc -l # output: '       3'
git tag -l        | wc -l # output: '       6'

# see stored refs
find refs       -type f | wc -l # output: '      20'
find refs/heads -type f | wc -l # output: '       3'
find refs/pull  -type f | wc -l # output: '      11'
find refs/tags  -type f | wc -l # output: '       6'

# see all remote refs
git ls-remote repo-to-fetch | wc -l                                      # output: '      24'
git ls-remote repo-to-fetch | grep HEAD | wc -l                          # output: '       1'
git ls-remote repo-to-fetch | grep "refs/heads" | wc -l                  # output: '       3'

git ls-remote repo-to-fetch | grep "refs/pull" | wc -l                   # output: '      11'
git ls-remote repo-to-fetch | grep "refs/pull/[0-9]\+/head" | wc -l      # output: '      10'
git ls-remote repo-to-fetch | grep "refs/pull/[0-9]\+/merge" | wc -l     # output: '       1'

git ls-remote repo-to-fetch | grep "refs/tags" | wc -l                   # output: '       9'
git ls-remote repo-to-fetch | grep "refs/tags" | grep -v "\^{}$" | wc -l # output: '       6'

# let's see how 'refs/pull/*' refspecs look like; let's assume we have
#   open pull request which have number ${prOpen}

# change N to the number of existing open pull request
prOpen=N

# the GitHub 'refs/pull/*/head' refspecs correspond to all created (open
#   and closed) pull requests; new 'refs/pull/<N>/head' is created every
#   time new pull request <N> is created (e.g. via GitHub webUI, 'gh', 'hub')
find refs/pull -type f | grep "refs/pull/[0-9]\+/head"  | wc -l # output: '      10'

# see how 'refs/pull/<N>/head' refspecs look like
cat refs/pull/${prOpen}/head # output: 'ce46a4519061e27250e1284523d8b3275f07248b'

git show $(cat refs/pull/${prOpen}/head) # output:
#> commit ce46a4519061e27250e1284523d8b3275f07248b (refs/pull/N/head, user/featureN)
#> Author: user <user@email.io>
#> Date:   Mon Apr 6 16:04:48 2020 +0300
#>
#>    featureN
#>
#> diff --git a/featureN b/featureN
#> new file mode 100644
#> index 0000000..e69de29

# the GitHub 'refs/pull/*/merge' refspecs correspond to open pull requests
#   only; new 'refs/pull/<N>/merge' is created every time new pull request
#   <N> is created (e.g. via GitHub webUI, 'gh', 'hub'); the
#   'refs/pull/<N>/merge' is deleted every time pull request <N> is
#   merged (e.g. via GitHub webUI, 'gh', 'hub')
find refs/pull -type f | grep "refs/pull/[0-9]\+/merge" | wc -l # output: '       1'

# see how 'refs/pull/<N>/merge' refspecs look like
cat refs/pull/${prOpen}/merge # output: '4ab972401e31c379d012e0c76bef97df8ec8e886'

git show $(cat refs/pull/${prOpen}/merge) # output:
#> commit 4ab972401e31c379d012e0c76bef97df8ec8e886 (refs/pull/N/merge)
#> Merge: 6937f49 ce46a45
#> Author: user <user@email.io>
#> Date:   Mon Apr 6 13:05:50 2020 +0000
#>
#>    Merge ce46a4519061e27250e1284523d8b3275f07248b into 6937f49a3f85b94c1caaa46245a0b9e02ffc23ff
#>

# let's see how 'refs/pull/*' are created/deleted as pull requests are
#   created/merged (e.g. via GitHub webUI, 'gh', 'hub'); let's assume the
#   next created pull request will have the number ${prNext}

# change M to the number of the next pull request (the number of
#   the last one plus one)
prNext=M

# look at the pull request locally and remotely
find refs/pull -type f -path "refs/pull/${prNext}/*"     # no output
git ls-remote repo-to-fetch | grep "refs/pull/${prNext}" # no output

# create and checkout to new branch 'user/featureM'
git branch user/feature${prNext}
mkdir ../work-tree
git --work-tree=../work-tree checkout user/feature${prNext}

# make, stage, and commit changes
touch ../work-tree/feature${prNext}
git --work-tree=../work-tree add feature${prNext}
git --work-tree=../work-tree commit -m "feature${prNext}"

# push the created branch to remote
git --work-tree=../work-tree push repo-to-fetch user/feature${prNext}

echo "here you NEED TO CREATE new branch pull request (e.g. via GitHub webUI)"
echo "the script will continue in 60 seconds"
sleep 60

# the GitHub Action refspecs (github.ref) for the created pull request
#   is 'refs/pull/M/merge'

# look at the pull request locally and remotely
find refs/pull -type f -path "refs/pull/${prNext}/*"     # no output
git ls-remote repo-to-fetch | grep "refs/pull/${prNext}" # output:
#> 71940958cc9ebf3904119ae16c549cc23cbe6652	refs/pull/M/head
#> 3c68ecbc55105bd7f9ecf67fb1692880fd7ae4a5	refs/pull/M/merge

# fetch and look at changes locally
git fetch repo-to-fetch
find refs/pull -type f -path "refs/pull/${prNext}/*" # output:
#> refs/pull/M/merge
#> refs/pull/M/head
find refs/pull -type f -path "refs/pull/${prNext}/*" | xargs cat # output:
#> 3c68ecbc55105bd7f9ecf67fb1692880fd7ae4a5
#> 71940958cc9ebf3904119ae16c549cc23cbe6652

echo "here you NEED TO MERGE the pull request (e.g. via GitHub webUI)"
echo "the script will continue in 60 seconds"
sleep 60

# the GitHub Action refspecs (github.ref) for the merge is 'refs/heads/master'

# look at the pull request locally and remotely
find refs/pull -type f -path "refs/pull/${prNext}/*" # output:
#> refs/pull/M/merge
#> refs/pull/M/head

git ls-remote repo-to-fetch | grep "refs/pull/${prNext}" # output:
#> 71940958cc9ebf3904119ae16c549cc23cbe6652	refs/pull/M/head

# fetch and look at changes locally
git fetch repo-to-fetch
find refs/pull -type f -path "refs/pull/${prNext}/*" # output:
#> refs/pull/M/merge
#> refs/pull/M/head

# remove any remote-tracking references (that no longer exist on the remote),
#   fetch and look at changes locally
git fetch repo-to-fetch -p
find refs/pull -type f -path "refs/pull/${prNext}/*" # output:
#> refs/pull/M/head

# PS: clean up local and remote repos

# remote feature branch is deleted after pull request merge

# see remote feature branch before it is deleted
git ls-remote repo-to-fetch | grep "feature${prNext}" # output:
#> 71940958cc9ebf3904119ae16c549cc23cbe6652	refs/heads/user/featureM

echo "here you NEED TO DELETE feature branch remotely (e.g. via GitHub webUI)"
echo "the script will continue in 60 seconds"
sleep 60

# no more remote feature branch after it is deleted
git ls-remote repo-to-fetch | grep "feature${prNext}" # no output

# local feature branch is also can be deleted after pull request merge

# see local feature branch before it is deleted
git br -a | grep "feature${prNext}" # output: '* user/featureM'

# delete feature branch locally
git br -d user/feature${prNext}

# no local feature branch after it is deleted
git br -a | grep "feature${prNext}" # no output

# [1] https://gist.github.com/piscisaureus/3342247