#!/usr/bin/env bash
#
# gitwatch - watch file or directory and git commit all changes as they happen
#
# Copyright (C) 2012  Patrick Lehner
#   with modifications and contributions by:
#   - Matthew McGowan
#
#############################################################################
#    This program is free software: you can redistribute it and/or modify
#    it under the terms of the GNU General Public License as published by
#    the Free Software Foundation, either version 3 of the License, or
#    (at your option) any later version.
#
#    This program is distributed in the hope that it will be useful,
#    but WITHOUT ANY WARRANTY; without even the implied warranty of
#    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
#    GNU General Public License for more details.
#
#    You should have received a copy of the GNU General Public License
#    along with this program.  If not, see <http://www.gnu.org/licenses/>.
#############################################################################
#
#   Idea and original code taken from http://stackoverflow.com/a/965274 
#       (but heavily modified by now)
#
#   Requires the command 'inotifywait' to be available, which is part of
#   the inotify-tools (See https://github.com/rvoicilas/inotify-tools ),
#   and (obviously) git
#

REMOTE=""
BRANCH="master"

shelp () { # Print a message about how to use this script
    echo "gitwatch - watch file or directory and git commit all changes as they happen"
    echo ""
    echo "Usage:"
    echo "${0##*/} [-p <remote> [-b <branch>]] <target>"
    echo ""
    echo "Where <target> is the file or folder which should be watched. The target needs"
    echo "to be in a Git repository; or in the case of a folder, it may also be the top"
    echo "folder of the repo."
    echo "The optional <remote> and <branch> define the arguments used for 'git push',"
    echo "which will be automatically done after each commit, if at least the -p option"
    echo "is specified."
}

while getopts b:hp: option 
do 
    case "${option}" in 
        b) BRANCH=${OPTARG};;
        h) shelp; exit;;
        p) REMOTE=${OPTARG};;
    esac
done

shift $((OPTIND-1)) # Shift the input arguments, so that the input file (last arg) is $1 in the code below

if [ $# -ne 1 ]; then
    shelp
    exit
fi

# Check for both git and inotifywait and generate an error
# if either don't exist or you cannot run them

if ! which git &>/dev/null; then
    echo >&2 "Git not found and it is required to use this script."
    exit 1

fi
if ! which inotifywait &>/dev/null; then
    echo >&2 "inotifywait not found and it is required to use this script."
    exit 1
fi

# These two strings are used to construct the commit comment
#  They're glued together like "<CCPREPEND>(<DATE&TIME>)<CCAPPEND>"
# If you don't want to add text before and/or after the date/time, simply
#  set them to empty strings
CCPREPEND="Scripted auto-commit on change "
CCAPPEND=" by gitwatch.sh"

IN=$(readlink -f "$1")

if [ -d $1 ]; then
    TARGETDIR=$(sed -e "s/\/*$//" <<<"$IN") # dir to CD into before using git commands: trim trailing slash, if any
    INCOMMAND="inotifywait --exclude=\"^${TARGETDIR}/.git\" -qqr -e close_write,moved_to,delete $TARGETDIR" # construct inotifywait-commandline
    GITADD="." # add "." (CWD) recursively to index
    GITINCOMMAND="-a" # add -a switch to "commit" call just to be sure
elif [ -f $1 ]; then
    TARGETDIR=${IN%/*} # dir to CD into before using git commands: extract from file name
    INCOMMAND="inotifywait -qq -e close_write,moved_to,delete $IN" # construct inotifywait-commandline
    GITADD="$IN" # add only the selected file to index
    GITINCOMMAND="" # no need to add anything more to "commit" call
else
    echo >&2 "Error: The target is neither a regular file nor a directory."
    exit 1
fi

while true; do
    $INCOMMAND # wait for changes
    sleep 2 # wait 2 more seconds to give apps time to write out all changes
    DATE=$(date "+%Y-%m-%d %H:%M:%S") # construct date-time string
    cd $TARGETDIR # CD into right dir
    git add $GITADD # add file(s) to index
    git commit $GITINCOMMAND -m"${CCPREPEND}(${DATE})${CCAPPEND}" # construct commit message and commit

    if [ -n "$REMOTE" ]; then # are we pushing to a remote?
       if [ -z "$BRANCH" ]; then # Do we have a branch set to push to ?
           git push $REMOTE # Branch not set, push to remote without a branch
       else
           git push $REMOTE $BRANCH # Branch set, push to the remote with the given branch
       fi
    fi
done