#!/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.
#
# Exit code
# ---------
# The script uses the following exit code:
# 0 : the script has been executed as expected, no errors have been encountered
# 124 : the script has taken too much time to execute and a timeout has been triggered

# ---------------------------- 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/}
			;;
		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

	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
        
	# Author list (unique, separted by comma)
	authors=""
	if [ ${change_type} = "update" ]; then
		authors=$(git log --pretty='format:%an' $oldrev..$newrev | sort -u | tr "\n" "," | sed -e 's/,$//' -e 's/,/, /g')
		authors="by $authors"
	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
	${emailprefix}$refname_type $short_refname ${change_type}d $authors
	X-Git-Refname:$refname
	X-Git-Reftype:$refname_type
	X-Git-Oldrev:$oldrev
	X-Git-Newrev:$newrev
	The $refname_type, $short_refname has been ${change_type}d
	EOF
}

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

	--${SPACE}
	This is an automated email from the git hooks/post-receive script. It was
	generated because a ref change was pushed to the repository containing
	the project "$projectdesc".
	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()
{
	timeout "$MAX_COMMAND_EXECUTION_TIME" \
	    "$(dirname $0)/post-receive-email-generate-update-branch-email" \
	        "$change_type" "$newrev" "$oldrev" "$refname" "$custom_showrev" "$oldrev_type" "$LOGBEGIN" "$LOGEND"

	if [ "$?" -eq "$TIMEOUT_EXIT_CODE" ]; then
	    echo "The summary of changes in the updated branch has taken too much time to be generated and was truncated"
	    exit_status=${TIMEOUT_EXIT_CODE}
	fi
}

#
# 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()
{
	timeout "$MAX_COMMAND_EXECUTION_TIME" \
	    "$(dirname $0)/post-receive-email-show-new-revision" "$change_type" "$newrev" "$oldrev" "$refname" "$custom_showrev"

	if [ "$?" -eq "$TIMEOUT_EXIT_CODE" ]; then
	    echo "The list of the new revisions has taken too much time to be generated and was truncated"
	    exit_status=${TIMEOUT_EXIT_CODE}
	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="-----------------------------------------------------------------------"
MAX_COMMAND_EXECUTION_TIME='5s'
TIMEOUT_EXIT_CODE=124

# --- 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")
# 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

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

exit_status=0

# Expect 3 parameters: oldrev newrev refname
if [ -n "$1" -a -n "$2" -a -n "$3" ]; then
	prep_for_email $1 $2 $3 || continue
	generate_email $maxlines
fi

exit ${exit_status}