hooks/post-receive-email

#!/bin/sh
#
# Copyright (c) 2007 Andy Parkins
#
# An example hook script to mail out commit update information.  This hook
# sends emails listing new revisions to the repository introduced by the
# change being reported.  The rule is that (for branch updates) each commit
# will appear on one email and one email only.
#
# This hook is stored in the contrib/hooks directory.  Your distribution
# will have put this somewhere standard.  You should make this script
# executable then link to it in the repository you would like to use it in.
# For example, on debian the hook is stored in
# /usr/share/doc/git-core/contrib/hooks/post-receive-email:
#
#  chmod a+x post-receive-email
#  cd /path/to/your/repository.git
#  ln -sf /usr/share/doc/git-core/contrib/hooks/post-receive-email hooks/post-receive
#
# This hook script assumes it is enabled on the central repository of a
# project, with all users pushing only to it and not between each other.  It
# will still work if you don't operate in that style, but it would become
# possible for the email to be from someone other than the person doing the
# push.
#
# To help with debugging and use on pre-v1.5.1 git servers, this script will
# also obey the interface of hooks/update, taking its arguments on the
# command line.  Unfortunately, hooks/update is called once for each ref.
# To avoid firing one email per ref, this script just prints its output to
# the screen when used in this mode.  The output can then be redirected if
# wanted.
#
# Config
# ------
# hooks.mailinglist
#   This is the list that all pushes will go to; leave it blank to not send
#   emails for every ref update.
# hooks.announcelist
#   This is the list that all pushes of annotated tags will go to.  Leave it
#   blank to default to the mailinglist field.  The announce emails lists
#   the short log summary of the changes since the last annotated tag.
# hooks.envelopesender
#   If set then the -f option is passed to sendmail to allow the envelope
#   sender address to be set
# hooks.emailprefix
#   All emails have their subjects prefixed with this prefix, or "[SCM]"
#   if emailprefix is unset, to aid filtering
# hooks.showrev
#   The shell command used to format each revision in the email, with
#   "%s" replaced with the commit id.  Defaults to "git rev-list -1
#   --pretty %s", displaying the commit id, author, date and log
#   message.  To list full patches separated by a blank line, you
#   could set this to "git show -C %s; echo".
#   To list a gitweb/cgit URL *and* a full patch for each change set, use this:
#     "t=%s; printf 'http://.../?id=%%s' \$t; echo;echo; git show -C \$t; echo"
#   Be careful if "..." contains things that will be expanded by shell "eval"
#   or printf.
# hooks.emailmaxlines
#   The maximum number of lines that should be included in the generated
#   email body. If not specified, there is no limit.
#   Lines beyond the limit are suppressed and counted, and a final
#   line is added indicating the number of suppressed lines.
#
# Notes
# -----
# All emails include the headers "X-Git-Refname", "X-Git-Oldrev",
# "X-Git-Newrev", and "X-Git-Reftype" to enable fine tuned filtering and
# give information for debugging.
#

# ---------------------------- Functions

#
# Function to prepare for email generation. This decides what type
# of update this is and whether an email should even be generated.
#
prep_for_email()
{
    # --- Arguments
    oldrev=$(git rev-parse $1)
    newrev=$(git rev-parse $2)
    refname="$3"
    maxlines=$4

    # --- Interpret
    # 0000->1234 (create)
    # 1234->2345 (update)
    # 2345->0000 (delete)
    if expr "$oldrev" : '0*$' >/dev/null
    then
        change_type="create"
    else
        if expr "$newrev" : '0*$' >/dev/null
        then
            change_type="delete"
        else
            change_type="update"
        fi
    fi

    # --- Get the revision types
    newrev_type=$(git cat-file -t $newrev 2> /dev/null)
    oldrev_type=$(git cat-file -t "$oldrev" 2> /dev/null)
    case "$change_type" in
    create|update)
        rev="$newrev"
        rev_type="$newrev_type"
        ;;
    delete)
        rev="$oldrev"
        rev_type="$oldrev_type"
        ;;
    esac

    # The revision type tells us what type the commit is, combined with
    # the location of the ref we can decide between
    #  - working branch
    #  - tracking branch
    #  - unannoted tag
    #  - annotated tag
    case "$refname","$rev_type" in
        refs/tags/*,commit)
            # un-annotated tag
            refname_type="tag"
            short_refname=${refname##refs/tags/}
            ;;
        refs/tags/*,tag)
            # annotated tag
            refname_type="annotated tag"
            short_refname=${refname##refs/tags/}
            # change recipients
            if [ -n "$announcerecipients" ]; then
                recipients="$announcerecipients"
            fi
            ;;
        refs/heads/*,commit)
            # branch
            refname_type="branch"
            short_refname=${refname##refs/heads/}
            ;;
        refs/remotes/*,commit)
            # tracking branch
            refname_type="tracking branch"
            short_refname=${refname##refs/remotes/}
            echo >&2 "*** Push-update of tracking branch, $refname"
            echo >&2 "***  - no email generated."
            return 1
            ;;
        *)
            # Anything else (is there anything else?)
            echo >&2 "*** Unknown type of update to $refname ($rev_type)"
            echo >&2 "***  - no email generated"
            return 1
            ;;
    esac

    # Check if we've got anyone to send to
    if [ -z "$recipients" ]; then
        case "$refname_type" in
            "annotated tag")
                config_name="hooks.announcelist"
                ;;
            *)
                config_name="hooks.mailinglist"
                ;;
        esac
        echo >&2 "*** $config_name is not set so no email will be sent"
        echo >&2 "*** for $refname update $oldrev->$newrev"
        return 1
    fi

    return 0
}

#
# Top level email generation function.  This calls the appropriate
# body-generation routine after outputting the common header.
#
# Note this function doesn't actually generate any email output, that is
# taken care of by the functions it calls:
#  - generate_email_header
#  - generate_create_XXXX_email
#  - generate_update_XXXX_email
#  - generate_delete_XXXX_email
#  - generate_email_footer
#
# Note also that this function cannot 'exit' from the script; when this
# function is running (in hook script mode), the send_mail() function
# is already executing in another process, connected via a pipe, and
# if this function exits without, whatever has been generated to that
# point will be sent as an email... even if nothing has been generated.
#
generate_email()
{
    # Email parameters
    # The email subject will contain the best description of the ref
    # that we can build from the parameters
    describe=$(git describe $rev 2>/dev/null)
    if [ -z "$describe" ]; then
        describe=$rev
    fi

    generate_email_header

    # Call the correct body generation function
    fn_name=general
    case "$refname_type" in
    "tracking branch"|branch)
        fn_name=branch
        ;;
    "annotated tag")
        fn_name=atag
        ;;
    esac

    if [ -z "$maxlines" ]; then
        generate_${change_type}_${fn_name}_email
    else
        generate_${change_type}_${fn_name}_email | limit_lines $maxlines
    fi

    generate_email_footer
}

generate_email_header()
{
    # --- Email (all stdout will be the email)
    # Generate header
    cat <<-EOF
    To: $recipients
    Subject: ${emailprefix}$projectdesc $refname_type $short_refname ${change_type}d. $describe
    X-Git-Refname: $refname
    X-Git-Reftype: $refname_type
    X-Git-Oldrev: $oldrev
    X-Git-Newrev: $newrev

    This is an automated email from the git hooks/post-receive script. It was
    generated because a ref change was pushed to the repository containing
    the project "$projectdesc".

    The $refname_type, $short_refname has been ${change_type}d
    EOF
}

generate_email_footer()
{
    SPACE=" "
    cat <<-EOF


    hooks/post-receive
    --${SPACE}
    $projectdesc
    EOF
}

# --------------- Branches

#
# Called for the creation of a branch
#
generate_create_branch_email()
{
    # This is a new branch and so oldrev is not valid
    echo "        at  $newrev ($newrev_type)"
    echo ""

    echo $LOGBEGIN
    show_new_revisions
    echo $LOGEND
}

#
# Called for the change of a pre-existing branch
#
generate_update_branch_email()
{
    # Consider this:
    #   1 --- 2 --- O --- X --- 3 --- 4 --- N
    #
    # O is $oldrev for $refname
    # N is $newrev for $refname
    # X is a revision pointed to by some other ref, for which we may
    #   assume that an email has already been generated.
    # In this case we want to issue an email containing only revisions
    # 3, 4, and N.  Given (almost) by
    #
    #  git rev-list N ^O --not --all
    #
    # The reason for the "almost", is that the "--not --all" will take
    # precedence over the "N", and effectively will translate to
    #
    #  git rev-list N ^O ^X ^N
    #
    # So, we need to build up the list more carefully.  git rev-parse
    # will generate a list of revs that may be fed into git rev-list.
    # We can get it to make the "--not --all" part and then filter out
    # the "^N" with:
    #
    #  git rev-parse --not --all | grep -v N
    #
    # Then, using the --stdin switch to git rev-list we have effectively
    # manufactured
    #
    #  git rev-list N ^O ^X
    #
    # This leaves a problem when someone else updates the repository
    # while this script is running.  Their new value of the ref we're
    # working on would be included in the "--not --all" output; and as
    # our $newrev would be an ancestor of that commit, it would exclude
    # all of our commits.  What we really want is to exclude the current
    # value of $refname from the --not list, rather than N itself.  So:
    #
    #  git rev-parse --not --all | grep -v $(git rev-parse $refname)
    #
    # Get's us to something pretty safe (apart from the small time
    # between refname being read, and git rev-parse running - for that,
    # I give up)
    #
    #
    # Next problem, consider this:
    #   * --- B --- * --- O ($oldrev)
    #          \
    #           * --- X --- * --- N ($newrev)
    #
    # That is to say, there is no guarantee that oldrev is a strict
    # subset of newrev (it would have required a --force, but that's
    # allowed).  So, we can't simply say rev-list $oldrev..$newrev.
    # Instead we find the common base of the two revs and list from
    # there.
    #
    # As above, we need to take into account the presence of X; if
    # another branch is already in the repository and points at some of
    # the revisions that we are about to output - we don't want them.
    # The solution is as before: git rev-parse output filtered.
    #
    # Finally, tags: 1 --- 2 --- O --- T --- 3 --- 4 --- N
    #
    # Tags pushed into the repository generate nice shortlog emails that
    # summarise the commits between them and the previous tag.  However,
    # those emails don't include the full commit messages that we output
    # for a branch update.  Therefore we still want to output revisions
    # that have been output on a tag email.
    #
    # Luckily, git rev-parse includes just the tool.  Instead of using
    # "--all" we use "--branches"; this has the added benefit that
    # "remotes/" will be ignored as well.

    # List all of the revisions that were removed by this update, in a
    # fast-forward update, this list will be empty, because rev-list O
    # ^N is empty.  For a non-fast-forward, O ^N is the list of removed
    # revisions
    fast_forward=""
    rev=""
    for rev in $(git rev-list $newrev..$oldrev)
    do
        revtype=$(git cat-file -t "$rev")
        echo "  discards  $rev ($revtype)"
    done
    if [ -z "$rev" ]; then
        fast_forward=1
    fi

    # List all the revisions from baserev to newrev in a kind of
    # "table-of-contents"; note this list can include revisions that
    # have already had notification emails and is present to show the
    # full detail of the change from rolling back the old revision to
    # the base revision and then forward to the new revision
    for rev in $(git rev-list $oldrev..$newrev)
    do
        revtype=$(git cat-file -t "$rev")
        echo "       via  $rev ($revtype)"
    done

    if [ "$fast_forward" ]; then
        echo "      from  $oldrev ($oldrev_type)"
    else
        #  1. Existing revisions were removed.  In this case newrev
        #     is a subset of oldrev - this is the reverse of a
        #     fast-forward, a rewind
        #  2. New revisions were added on top of an old revision,
        #     this is a rewind and addition.

        # (1) certainly happened, (2) possibly.  When (2) hasn't
        # happened, we set a flag to indicate that no log printout
        # is required.

        echo ""

        # Find the common ancestor of the old and new revisions and
        # compare it with newrev
        baserev=$(git merge-base $oldrev $newrev)
        rewind_only=""
        if [ "$baserev" = "$newrev" ]; then
            echo "This update discarded existing revisions and left the branch pointing at"
            echo "a previous point in the repository history."
            echo ""
            echo " * -- * -- N ($newrev)"
            echo "            \\"
            echo "             O -- O -- O ($oldrev)"
            echo ""
            echo "The removed revisions are not necessarilly gone - if another reference"
            echo "still refers to them they will stay in the repository."
            rewind_only=1
        else
            echo "This update added new revisions after undoing existing revisions.  That is"
            echo "to say, the old revision is not a strict subset of the new revision.  This"
            echo "situation occurs when you --force push a change and generate a repository"
            echo "containing something like this:"
            echo ""
            echo " * -- * -- B -- O -- O -- O ($oldrev)"
            echo "            \\"
            echo "             N -- N -- N ($newrev)"
            echo ""
            echo "When this happens we assume that you've already had alert emails for all"
            echo "of the O revisions, and so we here report only the revisions in the N"
            echo "branch from the common base, B."
        fi
    fi

    echo ""
    if [ -z "$rewind_only" ]; then
        echo "Those revisions listed above that are new to this repository have"
        echo "not appeared on any other notification email; so we list those"
        echo "revisions in full, below."

        echo ""
        echo $LOGBEGIN
        show_new_revisions

        # XXX: Need a way of detecting whether git rev-list actually
        # outputted anything, so that we can issue a "no new
        # revisions added by this update" message

        echo $LOGEND
    else
        echo "No new revisions were added by this update."
    fi

    # The diffstat is shown from the old revision to the new revision.
    # This is to show the truth of what happened in this change.
    # There's no point showing the stat from the base to the new
    # revision because the base is effectively a random revision at this
    # point - the user will be interested in what this revision changed
    # - including the undoing of previous revisions in the case of
    # non-fast-forward updates.
    echo ""
    echo "Summary of changes:"
    git diff-tree --stat --summary --find-copies-harder $oldrev..$newrev

    echo ""
    echo "Line of changes:"
    git diff --diff-filter=M --find-copies-harder --no-prefix --unified=2 $oldrev..$newrev
}

#
# Called for the deletion of a branch
#
generate_delete_branch_email()
{
    echo "       was  $oldrev"
    echo ""
    echo $LOGEND
    git show -s --pretty=oneline $oldrev
    echo $LOGEND
}

# --------------- Annotated tags

#
# Called for the creation of an annotated tag
#
generate_create_atag_email()
{
    echo "        at  $newrev ($newrev_type)"

    generate_atag_email
}

#
# Called for the update of an annotated tag (this is probably a rare event
# and may not even be allowed)
#
generate_update_atag_email()
{
    echo "        to  $newrev ($newrev_type)"
    echo "      from  $oldrev (which is now obsolete)"

    generate_atag_email
}

#
# Called when an annotated tag is created or changed
#
generate_atag_email()
{
    # Use git for-each-ref to pull out the individual fields from the
    # tag
    eval $(git for-each-ref --shell --format='
    tagobject=%(*objectname)
    tagtype=%(*objecttype)
    tagger=%(taggername)
    tagged=%(taggerdate)' $refname
    )

    echo "   tagging  $tagobject ($tagtype)"
    case "$tagtype" in
    commit)

        # If the tagged object is a commit, then we assume this is a
        # release, and so we calculate which tag this tag is
        # replacing
        prevtag=$(git describe --abbrev=0 $newrev^ 2>/dev/null)

        if [ -n "$prevtag" ]; then
            echo "  replaces  $prevtag"
        fi
        ;;
    *)
        echo "    length  $(git cat-file -s $tagobject) bytes"
        ;;
    esac
    echo " tagged by  $tagger"
    echo "        on  $tagged"

    echo ""
    echo $LOGBEGIN

    # Show the content of the tag message; this might contain a change
    # log or release notes so is worth displaying.
    git cat-file tag $newrev | sed -e '1,/^$/d'

    echo ""
    case "$tagtype" in
    commit)
        # Only commit tags make sense to have rev-list operations
        # performed on them
        if [ -n "$prevtag" ]; then
            # Show changes since the previous release
            git rev-list --pretty=short "$prevtag..$newrev" | git shortlog
        else
            # No previous tag, show all the changes since time
            # began
            git rev-list --pretty=short $newrev | git shortlog
        fi
        ;;
    *)
        # XXX: Is there anything useful we can do for non-commit
        # objects?
        ;;
    esac

    echo $LOGEND
}

#
# Called for the deletion of an annotated tag
#
generate_delete_atag_email()
{
    echo "       was  $oldrev"
    echo ""
    echo $LOGEND
    git show -s --pretty=oneline $oldrev
    echo $LOGEND
}

# --------------- General references

#
# Called when any other type of reference is created (most likely a
# non-annotated tag)
#
generate_create_general_email()
{
    echo "        at  $newrev ($newrev_type)"

    generate_general_email
}

#
# Called when any other type of reference is updated (most likely a
# non-annotated tag)
#
generate_update_general_email()
{
    echo "        to  $newrev ($newrev_type)"
    echo "      from  $oldrev"

    generate_general_email
}

#
# Called for creation or update of any other type of reference
#
generate_general_email()
{
    # Unannotated tags are more about marking a point than releasing a
    # version; therefore we don't do the shortlog summary that we do for
    # annotated tags above - we simply show that the point has been
    # marked, and print the log message for the marked point for
    # reference purposes
    #
    # Note this section also catches any other reference type (although
    # there aren't any) and deals with them in the same way.

    echo ""
    if [ "$newrev_type" = "commit" ]; then
        echo $LOGBEGIN
        git show --no-color --root -s --pretty=medium $newrev
        echo $LOGEND
    else
        # What can we do here?  The tag marks an object that is not
        # a commit, so there is no log for us to display.  It's
        # probably not wise to output git cat-file as it could be a
        # binary blob.  We'll just say how big it is
        echo "$newrev is a $newrev_type, and is $(git cat-file -s $newrev) bytes long."
    fi
}

#
# Called for the deletion of any other type of reference
#
generate_delete_general_email()
{
    echo "       was  $oldrev"
    echo ""
    echo $LOGEND
    git show -s --pretty=oneline $oldrev
    echo $LOGEND
}


# --------------- Miscellaneous utilities

#
# Show new revisions as the user would like to see them in the email.
#
show_new_revisions()
{
    # This shows all log entries that are not already covered by
    # another ref - i.e. commits that are now accessible from this
    # ref that were previously not accessible
    # (see generate_update_branch_email for the explanation of this
    # command)

    # Revision range passed to rev-list differs for new vs. updated
    # branches.
    if [ "$change_type" = create ]
    then
        # Show all revisions exclusive to this (new) branch.
        revspec=$newrev
    else
        # Branch update; show revisions not part of $oldrev.
        revspec=$oldrev..$newrev
    fi

    other_branches=$(git for-each-ref --format='%(refname)' refs/heads/ |
        grep -F -v $refname)
    git rev-parse --not $other_branches |
    if [ -z "$custom_showrev" ]
    then
        git rev-list --pretty --stdin $revspec
    else
        git rev-list --stdin $revspec |
        while read onerev
        do
            eval $(printf "$custom_showrev" $onerev)
        done
    fi
}


limit_lines()
{
    lines=0
    skipped=0
    while IFS="" read -r line; do
        lines=$((lines + 1))
        if [ $lines -gt $1 ]; then
            skipped=$((skipped + 1))
        else
            printf "%s\n" "$line"
        fi
    done
    if [ $skipped -ne 0 ]; then
        echo "... $skipped lines suppressed ..."
    fi
}


send_mail()
{
    if [ -n "$envelopesender" ]; then
        /usr/sbin/sendmail -t -f "$envelopesender"
    else
        /usr/sbin/sendmail -t
    fi
}

# ---------------------------- main()

# --- Constants
LOGBEGIN="- Log -----------------------------------------------------------------"
LOGEND="-----------------------------------------------------------------------"

# --- Config
# Set GIT_DIR either from the working directory, or from the environment
# variable.
GIT_DIR=$(git rev-parse --git-dir 2>/dev/null)
if [ -z "$GIT_DIR" ]; then
    echo >&2 "fatal: post-receive: GIT_DIR not set"
    exit 1
fi

projectdesc=$(sed -ne '1p' "$GIT_DIR/description" 2>/dev/null)
# Check if the description is unchanged from it's default, and shorten it to
# a more manageable length if it is
if expr "$projectdesc" : "Unnamed repository.*$" >/dev/null
then
    projectdesc="UNNAMED PROJECT"
fi

recipients=$(git config hooks.mailinglist)
announcerecipients=$(git config hooks.announcelist)
envelopesender=$(git config hooks.envelopesender)
emailprefix=$(git config hooks.emailprefix || echo '[SCM] ')
custom_showrev=$(git config hooks.showrev)
maxlines=$(git config hooks.emailmaxlines)

# --- Main loop
# Allow dual mode: run from the command line just like the update hook, or
# if no arguments are given then run as a hook script
if [ -n "$1" -a -n "$2" -a -n "$3" ]; then
    # Output to the terminal in command line mode - if someone wanted to
    # resend an email; they could redirect the output to sendmail
    # themselves
    prep_for_email $2 $3 $1 && PAGER= generate_email
else
    while read oldrev newrev refname
    do
        prep_for_email $oldrev $newrev $refname || continue
        generate_email $maxlines | send_mail
    done
fi