Edit File: update-hook-example.txt
From: Junio C Hamano <gitster@pobox.com> and Carl Baldwin <cnb@fc.hp.com> Subject: control access to branches. Date: Thu, 17 Nov 2005 23:55:32 -0800 Message-ID: <7vfypumlu3.fsf@assigned-by-dhcp.cox.net> Abstract: An example hooks/update script is presented to implement repository maintenance policies, such as who can push into which branch and who can make a tag. Content-type: text/asciidoc How to use the update hook ========================== When your developer runs git-push into the repository, git-receive-pack is run (either locally or over ssh) as that developer, so is hooks/update script. Quoting from the relevant section of the documentation: Before each ref is updated, if $GIT_DIR/hooks/update file exists and executable, it is called with three parameters: $GIT_DIR/hooks/update refname sha1-old sha1-new The refname parameter is relative to $GIT_DIR; e.g. for the master head this is "refs/heads/master". Two sha1 are the object names for the refname before and after the update. Note that the hook is called before the refname is updated, so either sha1-old is 0{40} (meaning there is no such ref yet), or it should match what is recorded in refname. So if your policy is (1) always require fast-forward push (i.e. never allow "git-push repo +branch:branch"), (2) you have a list of users allowed to update each branch, and (3) you do not let tags to be overwritten, then you can use something like this as your hooks/update script. [jc: editorial note. This is a much improved version by Carl since I posted the original outline] ---------------------------------------------------- #!/bin/bash umask 002 # If you are having trouble with this access control hook script # you can try setting this to true. It will tell you exactly # why a user is being allowed/denied access. verbose=false # Default shell globbing messes things up downstream GLOBIGNORE=* function grant { $verbose && echo >&2 "-Grant- $1" echo grant exit 0 } function deny { $verbose && echo >&2 "-Deny- $1" echo deny exit 1 } function info { $verbose && echo >&2 "-Info- $1" } # Implement generic branch and tag policies. # - Tags should not be updated once created. # - Branches should only be fast-forwarded unless their pattern starts with '+' case "$1" in refs/tags/*) git rev-parse --verify -q "$1" && deny >/dev/null "You can't overwrite an existing tag" ;; refs/heads/*) # No rebasing or rewinding if expr "$2" : '0*$' >/dev/null; then info "The branch '$1' is new..." else # updating -- make sure it is a fast-forward mb=$(git-merge-base "$2" "$3") case "$mb,$2" in "$2,$mb") info "Update is fast-forward" ;; *) noff=y; info "This is not a fast-forward update.";; esac fi ;; *) deny >/dev/null \ "Branch is not under refs/heads or refs/tags. What are you trying to do?" ;; esac # Implement per-branch controls based on username allowed_users_file=$GIT_DIR/info/allowed-users username=$(id -u -n) info "The user is: '$username'" if test -f "$allowed_users_file" then rc=$(cat $allowed_users_file | grep -v '^#' | grep -v '^$' | while read heads user_patterns do # does this rule apply to us? head_pattern=${heads#+} matchlen=$(expr "$1" : "${head_pattern#+}") test "$matchlen" = ${#1} || continue # if non-ff, $heads must be with the '+' prefix test -n "$noff" && test "$head_pattern" = "$heads" && continue info "Found matching head pattern: '$head_pattern'" for user_pattern in $user_patterns; do info "Checking user: '$username' against pattern: '$user_pattern'" matchlen=$(expr "$username" : "$user_pattern") if test "$matchlen" = "${#username}" then grant "Allowing user: '$username' with pattern: '$user_pattern'" fi done deny "The user is not in the access list for this branch" done ) case "$rc" in grant) grant >/dev/null "Granting access based on $allowed_users_file" ;; deny) deny >/dev/null "Denying access based on $allowed_users_file" ;; *) ;; esac fi allowed_groups_file=$GIT_DIR/info/allowed-groups groups=$(id -G -n) info "The user belongs to the following groups:" info "'$groups'" if test -f "$allowed_groups_file" then rc=$(cat $allowed_groups_file | grep -v '^#' | grep -v '^$' | while read heads group_patterns do # does this rule apply to us? head_pattern=${heads#+} matchlen=$(expr "$1" : "${head_pattern#+}") test "$matchlen" = ${#1} || continue # if non-ff, $heads must be with the '+' prefix test -n "$noff" && test "$head_pattern" = "$heads" && continue info "Found matching head pattern: '$head_pattern'" for group_pattern in $group_patterns; do for groupname in $groups; do info "Checking group: '$groupname' against pattern: '$group_pattern'" matchlen=$(expr "$groupname" : "$group_pattern") if test "$matchlen" = "${#groupname}" then grant "Allowing group: '$groupname' with pattern: '$group_pattern'" fi done done deny "None of the user's groups are in the access list for this branch" done ) case "$rc" in grant) grant >/dev/null "Granting access based on $allowed_groups_file" ;; deny) deny >/dev/null "Denying access based on $allowed_groups_file" ;; *) ;; esac fi deny >/dev/null "There are no more rules to check. Denying access" ---------------------------------------------------- This uses two files, $GIT_DIR/info/allowed-users and allowed-groups, to describe which heads can be pushed into by whom. The format of each file would look like this: refs/heads/master junio +refs/heads/pu junio refs/heads/cogito$ pasky refs/heads/bw/.* linus refs/heads/tmp/.* .* refs/tags/v[0-9].* junio With this, Linus can push or create "bw/penguin" or "bw/zebra" or "bw/panda" branches, Pasky can do only "cogito", and JC can do master and pu branches and make versioned tags. And anybody can do tmp/blah branches. The '+' sign at the pu record means that JC can make non-fast-forward pushes on it.