#!/bin/sh
#
# An example hook script to mail out commit update information.
# It can also blocks tags that aren't annotated.
# Called by git-receive-pack with arguments: refname sha1-old sha1-new
#
# To enable this hook, make this file executable by "chmod +x update".
#
# Config
# ------
# hooks.mailinglist
#   This is the list that all pushes will go to; leave it blank to not send
#   emails frequently.  The log email will list every log entry in full between
#   the old ref value and the new ref value.
# hooks.announcelist
#   This is the list that all pushes of annotated tags will go to.  Leave it
#   blank to just use the mailinglist field.  The announce emails list the
#   short log summary of the changes since the last annotated tag
# hooks.allowunannotated
#   This boolean sets whether unannotated tags will be allowed into the
#   repository.  By default they won't be.
#
# Notes
# -----
# All emails have their subjects prefixed with "[SCM]" to aid filtering.
# All emails include the headers "X-Git-Refname", "X-Git-Oldrev",
# "X-Git-Newrev", and "X-Git-Reftype" to enable fine tuned filtering and info.

# --- Constants
EMAILPREFIX="[SCM] "
LOGBEGIN="- Log -----------------------------------------------------------------"
LOGEND="-----------------------------------------------------------------------"
DATEFORMAT="%F %R %z"

# --- Command line
refname="$1"
oldrev="$2"
newrev="$3"

# --- 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

if [ -z "$refname" -o -z "$oldrev" -o -z "$newrev" ]; then
        echo "Usage: $0 <ref> <oldrev> <newrev>" >&2
        exit 1
fi

# --- Config
projectdesc=$(cat $GIT_DIR/description)
recipients=$(git-repo-config hooks.mailinglist)
announcerecipients=$(git-repo-config hooks.announcelist)
allowunannotated=$(git-repo-config --bool hooks.allowunannotated)

# --- Check types
newrev_type=$(git-cat-file -t "$newrev")

case "$refname","$newrev_type" in
        refs/tags/*,commit)
                # un-annotated tag
                refname_type="tag"
                short_refname=${refname##refs/tags/}
                if [ "$allowunannotated" != "true" ]; then
                        echo "*** The un-annotated tag, $short_refname is not allowed in this repository" >&2
                        echo "*** Use 'git tag [ -a | -s ]' for tags you want to propagate." >&2
                        exit 1
                fi
                ;;
        refs/tags/*,tag)
                # annotated tag
                refname_type="annotated tag"
                short_refname=${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/}
                # Should this even be allowed?
                echo "*** Push-update of tracking branch, $refname.  No email generated." >&2
                exit 0
                ;;
        *)
                # Anything else (is there anything else?)
                echo "*** Update hook: unknown type of update, \"$newrev_type\", to ref $refname" >&2
                exit 1
                ;;
esac

# Check if we've got anyone to send to
if [ -z "$recipients" ]; then
        # If the email isn't sent, then at least give the user some idea of what command
        # would generate the email at a later date
        echo "*** No recipients found - no email will be sent, but the push will continue" >&2
        echo "*** for $0 $1 $2 $3" >&2
        exit 0
fi

# --- Email parameters
committer=$(git show --pretty=full -s $newrev | grep "^Commit: " | sed -e "s/^Commit: //")
describe=$(git describe $newrev 2>/dev/null)
if [ -z "$describe" ]; then
        describe=$newrev
fi

# --- Email (all stdout will be the email)
(
# Generate header
cat <<-EOF
From: $committer
To: $recipients
Subject: ${EMAILPREFIX}$projectdesc $refname_type, $short_refname now at $describe
X-Git-Refname: $refname
X-Git-Reftype: $refname_type
X-Git-Oldrev: $oldrev
X-Git-Newrev: $newrev

Hello,

This is an automated email from the git hooks/update script, it was
generated because a ref change was pushed to the repository.

Updating $refname_type, $short_refname,
EOF

case "$refname_type" in
        "tracking branch"|branch)
                if expr "$oldrev" : '0*$' >/dev/null
                then
                        # If the old reference is "0000..0000" then this is a new branch
                        # and so oldrev is not valid
                        echo "  as a new  $refname_type"
                    echo "        to  $newrev ($newrev_type)"
                        echo ""
                        echo $LOGBEGIN
                        # 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
                        git-rev-parse --not --all | git-rev-list --stdin --pretty $newref
                        echo $LOGEND
                else
                        # oldrev is valid
                        oldrev_type=$(git-cat-file -t "$oldrev")

                        # Now the problem is for cases like this:
                        #   * --- * --- * --- * (oldrev)
                        #          \
                        #           * --- * --- * (newrev)
                        # i.e. there is no guarantee that newrev is a strict subset
                        # of oldrev - (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
                        baserev=$(git-merge-base $oldrev $newrev)

                        # Commit with a parent
                        for rev in $(git-rev-list $newrev ^$baserev)
                        do
                                revtype=$(git-cat-file -t "$rev")
                                echo "       via  $rev ($revtype)"
                        done
                        if [ "$baserev" = "$oldrev" ]; then
                                echo "      from  $oldrev ($oldrev_type)"
                        else
                                echo "  based on  $baserev"
                                echo "      from  $oldrev ($oldrev_type)"
                                echo ""
                                echo "This ref update crossed a branch point; i.e. the old rev is not a strict subset"
                                echo "of the new rev.  This occurs, when you --force push a change in a situation"
                                echo "like this:"
                                echo ""
                                echo " * -- * -- B -- O -- O -- O ($oldrev)"
                                echo "            \\"
                                echo "             N -- N -- N ($newrev)"
                                echo ""
                                echo "Therefore, we assume that you've already had alert emails for all of the O"
                                echo "revisions, and now give you all the revisions in the N branch from the common"
                                echo "base, B ($baserev), up to the new revision."
                        fi
                        echo ""
                        echo $LOGBEGIN
                        git-rev-list --pretty $newrev ^$baserev
                        echo $LOGEND
                        echo ""
                        echo "Diffstat:"
                        git-diff-tree --no-color --stat -M -C --find-copies-harder $newrev ^$baserev
                fi
                ;;
        "annotated tag")
                # Should we allow changes to annotated tags?
                if expr "$oldrev" : '0*$' >/dev/null
                then
                        # If the old reference is "0000..0000" then this is a new atag
                        # and so oldrev is not valid
                        echo "        to  $newrev ($newrev_type)"
                else
                        echo "        to  $newrev ($newrev_type)"
                        echo "      from  $oldrev"
                fi

                # If this tag succeeds another, then show which tag it replaces
                prevtag=$(git describe $newrev^ 2>/dev/null | sed 's/-g.*//')
                if [ -n "$prevtag" ]; then
                        echo "  replaces  $prevtag"
                fi

                # Read the tag details
                eval $(git cat-file tag $newrev | \
                        sed -n '4s/tagger \([^>]*>\)[^0-9]*\([0-9]*\).*/tagger="\1" ts="\2"/p')
                tagged=$(date --date="1970-01-01 00:00:00 +0000 $ts seconds" +"$DATEFORMAT")

                echo " tagged by  $tagger"
                echo "        on  $tagged"

                echo ""
                echo $LOGBEGIN
                echo ""

                if [ -n "$prevtag" ]; then
                        git rev-list --pretty=short "$prevtag..$newrev" | git shortlog
                else
                        git rev-list --pretty=short $newrev | git shortlog
                fi

                echo $LOGEND
                echo ""
                ;;
        *)
                # By default, unannotated tags aren't allowed in; if
                # they are though, it's debatable whether we would even want an
                # email to be generated; however, I don't want to add another config
                # option just for that.
                #
                # Unannotated tags are more about marking a point than releasing
                # a version; therefore we don't do the shortlog summary that we
                # do for annotated tags above - we simply show that the point has
                # been marked, and print the log message for the marked point for
                # reference purposes
                #
                # Note this section also catches any other reference type (although
                # there aren't any) and deals with them in the same way.
                if expr "$oldrev" : '0*$' >/dev/null
                then
                        # If the old reference is "0000..0000" then this is a new tag
                        # and so oldrev is not valid
                        echo "  as a new  $refname_type"
                        echo "        to  $newrev ($newrev_type)"
                else
                        echo "        to  $newrev ($newrev_type)"
                        echo "      from  $oldrev"
                fi
                echo ""
                echo $LOGBEGIN
                git-show --no-color --root -s $newrev
                echo $LOGEND
                echo ""
                ;;
esac

# Footer
cat <<-EOF

hooks/update
---
Git Source Code Management System
$0 $1 \\
  $2 \\
  $3
EOF
#) | cat >&2
) | /usr/sbin/sendmail -t

# --- Finished
exit 0