Is it possible do git commit on server side update hook - bash

Question

Point of my task : gather info about repo and place it to file while update hook and commit it ( perfectly with new commit).
Problems : when I'm doing commit -> it lockes origin repository and after this push is failing. my code looks like this :
#!/bin/bash
# --- Command line
refname="$1"
oldrev="$2"
newrev="$3"
export GIT_WORK_TREE=$PWD
# --- Safety check
if [ -z "$GIT_DIR" ]; then
echo "Don't run this script from the command line." >&2
echo " (if you want, you could supply GIT_DIR then run" >&2
echo " $0 <ref> <oldrev> <newrev>)" >&2
exit 1
fi
version="${refname##*_}"
branchName="${refname##*/}"
filePath="_componentVersion/BranchVersion.ps1"
if [ -z "$refname" -o -z "$oldrev" -o -z "$newrev" ]; then
echo "usage: $0 <ref> <oldrev> <newrev>" >&2
exit 1
fi
# --- Check types
# if $newrev is 0000...0000, it's a commit to delete a ref.
zero="0000000000000000000000000000000000000000"
if [ "$newrev" = "$zero" ]; then
newrev_type=delete
else
newrev_type=$(git cat-file -t $newrev)
fi
case "$refname","$newrev_type" in
refs/heads/*,commit)
if [ "$oldrev " != "$zero" ]; then
version="${refname##*_}"
branchName="${refname##*/}"
filePath="_componentVersion/BranchVersion.ps1"
countOfCommits=$(git rev-list --count START_$version..$newrev)
countOfPushes=$(git log --pretty=oneline START_$version..$newrev | grep 'Issue nr: HOOK_$version' | wc -l)
countOfPushes=$(($countOfPushes+1))
echo git log --pretty=oneline START_$version..$newrev
message="
# -----------------------
# Brancht Version Info
# -----------------------
\$branch = '$version'
\$countOfCommits = $countOfCommits
\$countOfPushes = $countOfPushes # push
\$commitHash = '$newrev'
"
# credits go to https://stackoverflow.com/questions/9670302/commit-directly-to-a-bare-repository
# branch commit - here we will do the magic about count of commits and about count of pushes
# here we create file for info
# Empty the index, not sure if this step is necessary
git read-tree --empty
# Load the current tree. A commit ref is fine, it'll figure it out.
git read-tree "${newrev}"
# create blob from stdin
BLOB_ID=$(echo "$message" | git hash-object -w --stdin)
# update indexes in git
git update-index --add --cacheinfo 100644 "$BLOB_ID" "$filePath"
# Create a tree from your new index
TREE_ID=$(git write-tree)
# Commit it.
NEW_COMMIT=$(echo "Issue nr: HOOK_$version $message" | git commit-tree "$TREE_ID" -p "$oldrev")
# Update the branch
git update-ref "$refname" "$NEW_COMMIT" "$oldrev"
fi
# Done
exit 0
;;
*)
# Other actions except commit to branch / for now - we won't check it
exit 0
;;
esac
# --- Finished
exit 0
I'm working with bare repo. And example of commit taken from here
Execte problem is
remote: error: cannot lock ref 'refs/heads/REL_7.0.0': ref refs/heads/REL_7.0.0 is at 54f2454ddab36eda001e27946733a7b0e981f097 but expected 89a3032e0bfb999273205e32b7f6d57173c4bd7e

Answer 1

You can create commits.
You cannot update references that are locked, which includes the one that the update hook is being called for.
Since git push can push multiple reference names, there may be additional locked references. In general it's not a good idea to update anything that anyone might be git pushing inside a hook invoked by git push. In other words, don't try to update any branch or tag name. If you want to create new objects, attach them to some name outside these two name-spaces.
(Aside: the git read-tree --empty is not necessary, but it's a good idea to use a temporary index file anyway, rather than using the main index.)