gitwatch/gitwatch.sh

#!/usr/bin/env bash
#
# gitwatch - watch file or directory and git commit all changes as they happen
#
# Copyright (C) 2013-2018  Patrick Lehner
#   with modifications and contributions by:
#   - Matthew McGowan
#   - Dominik D. Geyer
#   - Phil Thompson
#   - Dave Musicant
#
#############################################################################
#    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
#       original work by Lester Buck
#       (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.
#   Will check the availability of both commands using the `which` command
#   and will abort if either command (or `which`) is not found.
#

REMOTE=""
BRANCH=""
SLEEP_TIME=2
DATE_FMT="+%Y-%m-%d %H:%M:%S"
COMMITMSG="Scripted auto-commit on change (%d) by gitwatch.sh"
LISTCHANGES=-1
LISTCHANGES_COLOR="--color=always"
GIT_DIR=""

# Print a message about how to use this script
shelp () {
    echo "gitwatch - watch file or directory and git commit all changes as they happen"
    echo ""
    echo "Usage:"
    echo "${0##*/} [-s <secs>] [-d <fmt>] [-r <remote> [-b <branch>]]"
    echo "          [-m <msg>] [-l|-L <lines>] <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 ""
    echo " -s <secs>        After detecting a change to the watched file or directory,"
    echo "                  wait <secs> seconds until committing, to allow for more"
    echo "                  write actions of the same batch to finish; default is 2sec"
    echo " -d <fmt>         The format string used for the timestamp in the commit"
    echo "                  message; see 'man date' for details; default is "
    echo "                  \"+%Y-%m-%d %H:%M:%S\""
    echo " -r <remote>      If given and non-empty, a 'git push' to the given <remote>"
    echo "                  is done after every commit; default is empty, i.e. no push"
    echo " -b <branch>      The branch which should be pushed automatically;"
    echo "                - if not given, the push command used is  'git push <remote>',"
    echo "                    thus doing a default push (see git man pages for details)"
    echo "                - if given and"
    echo "                  + repo is in a detached HEAD state (at launch)"
    echo "                    then the command used is  'git push <remote> <branch>'"
    echo "                  + repo is NOT in a detached HEAD state (at launch)"
    echo "                    then the command used is"
    echo "                    'git push <remote> <current branch>:<branch>'  where"
    echo "                    <current branch> is the target of HEAD (at launch)"
    echo "                  if no remote was defined with -r, this option has no effect"
    echo " -g <path>        Location of the .git directory, if stored elsewhere in"
    echo "                  a remote location. This specifies the --git-dir parameter"
    echo " -l <lines>       Log the actual changes made in this commit, up to a given"
    echo "                  number of lines, or all lines if 0 is given"
    echo " -L <lines>       Same as -l but without colored formatting"
    echo " -m <msg>         The commit message used for each commit; all occurrences of"
    echo "                  %d in the string will be replaced by the formatted date/time"
    echo "                  (unless the <fmt> specified by -d is empty, in which case %d"
    echo "                  is replaced by an empty string); the default message is:"
    echo "                  \"Scripted auto-commit on change (%d) by gitwatch.sh\""
    echo " -e <events>      Events passed to inotifywait to watch (defaults to "
    echo "                  '$EVENTS')"
    echo "                  (useful when using inotify-win, e.g. -e modify,delete,move)"
    echo "                  (currently ignored on Mac, which only uses default values)"
    echo ""
    echo "As indicated, several conditions are only checked once at launch of the"
    echo "script. You can make changes to the repo state and configurations even while"
    echo "the script is running, but that may lead to undefined and unpredictable (even"
    echo "destructive) behavior!"
    echo "It is therefore recommended to terminate the script before changing the repo's"
    echo "config and restarting it afterwards."
    echo ""
    echo "By default, gitwatch tries to use the binaries \"git\", \"inotifywait\", and"
    echo "\"readline\", expecting to find them in the PATH (it uses 'which' to check this"
    echo "and will abort with an error if they cannot be found). If you want to use"
    echo "binaries that are named differently and/or located outside of your PATH, you can"
    echo "define replacements in the environment variables GW_GIT_BIN, GW_INW_BIN, and"
    echo "GW_RL_BIN for git, inotifywait, and readline, respectively."
}

# print all arguments to stderr
stderr () {
    echo $@ >&2
}

# clean up at end of program, killing the remaining sleep process if it still exists
cleanup () {
    if [[ -n "$SLEEP_PID" ]] && kill -0 "$SLEEP_PID" &>/dev/null; then
        kill "$SLEEP_PID" &>/dev/null
    fi
    exit 0
}

# Tests for the availability of a command
is_command () {
	hash "$1" 2>/dev/null
}

###############################################################################

while getopts b:d:h:g:L:l:m:p:r:s:e: option # Process command line options
do
    case "${option}" in
        b) BRANCH=${OPTARG};;
        d) DATE_FMT=${OPTARG};;
        h) shelp; exit;;
        g) GIT_DIR=${OPTARG};;
        l) LISTCHANGES=${OPTARG};;
        L) LISTCHANGES=${OPTARG}; LISTCHANGES_COLOR="";;
        m) COMMITMSG=${OPTARG};;
        p|r) REMOTE=${OPTARG};;
        s) SLEEP_TIME=${OPTARG};;
        e) EVENTS=${OPTARG};;
        *) stderr "Error: Option '${option}' does not exist."; shelp; exit 1;;
    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 # If no command line arguments are left (that's bad: no target was passed)
    shelp # print usage help
    exit # and exit
fi

# if custom bin names are given for git, inotifywait, or readlink, use those; otherwise fall back to "git", "inotifywait", and "readlink"
if [ -z "$GW_GIT_BIN" ]; then GIT="git"; else GIT="$GW_GIT_BIN"; fi

if [ -z "$GW_INW_BIN" ]; then
    # if Mac, use fswatch
    if [ "$(uname)" != "Darwin" ]; then
        INW="inotifywait";
        EVENTS="${EVENTS:-close_write,move,move_self,delete,create,modify}"
    else
        INW="fswatch";
        # default events specified via a mask, see
        # https://emcrisostomo.github.io/fswatch/doc/1.14.0/fswatch.html/Invoking-fswatch.html#Numeric-Event-Flags
        # default of 414 = MovedTo + MovedFrom + Renamed + Removed + Updated + Created
        #                = 256 + 128+ 16 + 8 + 4 + 2
        EVENTS="${EVENTS:---event=414}"
    fi;
else
    INW="$GW_INW_BIN";
fi

if [ -z "$GW_RL_BIN" ]; then RL="readlink"; else RL="$GW_RL_BIN"; fi

# Check availability of selected binaries and die if not met
for cmd in "$GIT" "$INW"; do
	is_command "$cmd" || { stderr "Error: Required command '$cmd' not found." ; exit 2; }
done
unset cmd

###############################################################################

SLEEP_PID="" # pid of timeout subprocess

trap "cleanup" EXIT # make sure the timeout is killed when exiting script


# Expand the path to the target to absolute path
if [ "$(uname)" != "Darwin" ]; then
    IN=$($RL -f "$1")
else
    if is_command "greadlink"; then
      IN=$(greadlink -f "$1")
    else
      IN=$($RL -f "$1")
      if [ $? -eq 1 ]; then
        echo "Seems like your readlink doesn't support '-f'. Running without. Please 'brew install coreutils'."
        IN=$($RL "$1")
      fi
    fi;
fi;


if [ -d "$1" ]; then # if the target is a directory

    TARGETDIR=$(sed -e "s/\/*$//" <<<"$IN") # dir to CD into before using git commands: trim trailing slash, if any
    # construct inotifywait-commandline
    if [ "$(uname)" != "Darwin" ]; then
        INW_ARGS=("-qmr" "-e" "$EVENTS" "--exclude" "'(\.git/|\.git$)'" "\"$TARGETDIR\"")
    else
        # still need to fix EVENTS since it wants them listed one-by-one
        INW_ARGS=("--recursive" "$EVENTS" "-E" "--exclude" "'(\.git/|\.git$)'" "\"$TARGETDIR\"")
    fi;
    GIT_ADD_ARGS="--all ." # add "." (CWD) recursively to index
    GIT_COMMIT_ARGS="" # add -a switch to "commit" call just to be sure

elif [ -f "$1" ]; then # if the target is a single file

    TARGETDIR=$(dirname "$IN") # dir to CD into before using git commands: extract from file name
    # construct inotifywait-commandline
    if [ "$(uname)" != "Darwin" ]; then
        INW_ARGS=("-qm" "-e" "$EVENTS" "$IN")
    else
        INW_ARGS=("$EVENTS" "$IN")
    fi

    GIT_ADD_ARGS="$IN" # add only the selected file to index
    GIT_COMMIT_ARGS="" # no need to add anything more to "commit" call
else
    stderr "Error: The target is neither a regular file nor a directory."
    exit 3
fi

# If $GIT_DIR is set, verify that it is a directory, and then add parameters to
# git command as need be
if [ -n "$GIT_DIR" ]; then

    if [ ! -d "$GIT_DIR" ]; then
        stderr ".git location is not a directory: $GIT_DIR";
        exit 4;
    fi

    GIT="$GIT --no-pager --work-tree $TARGETDIR --git-dir $GIT_DIR"
fi

# Check if commit message needs any formatting (date splicing)
if ! grep "%d" > /dev/null <<< "$COMMITMSG"; then # if commitmsg didn't contain %d, grep returns non-zero
    DATE_FMT="" # empty date format (will disable splicing in the main loop)
    FORMATTED_COMMITMSG="$COMMITMSG" # save (unchanging) commit message
fi

# CD into right dir
cd "$TARGETDIR" || { stderr "Error: Can't change directory to '${TARGETDIR}'." ; exit 5; }

if [ -n "$REMOTE" ]; then # are we pushing to a remote?
    if [ -z "$BRANCH" ]; then # Do we have a branch set to push to ?
        PUSH_CMD="$GIT push $REMOTE" # Branch not set, push to remote without a branch
    else
        # check if we are on a detached HEAD
        if HEADREF=$($GIT symbolic-ref HEAD 2> /dev/null); then # HEAD is not detached
            PUSH_CMD="$GIT push $REMOTE $(sed "s_^refs/heads/__" <<< "$HEADREF"):$BRANCH"
        else # HEAD is detached
            PUSH_CMD="$GIT push $REMOTE $BRANCH"
        fi
    fi
else
    PUSH_CMD="" # if not remote is selected, make sure push command is empty
fi

# A function to reduce git diff output to the actual changed content, and insert file line numbers.
# Based on "https://stackoverflow.com/a/12179492/199142" by John Mellor
diff-lines() {
    local path=
    local line=
    local previous_path=
    while read; do
        esc=$'\033'
        if [[ $REPLY =~ ---\ (a/)?([^[:blank:]$esc]+).* ]]; then
            previous_path=${BASH_REMATCH[2]}
            continue
        elif [[ $REPLY =~ \+\+\+\ (b/)?([^[:blank:]$esc]+).* ]]; then
            path=${BASH_REMATCH[2]}
        elif [[ $REPLY =~ @@\ -[0-9]+(,[0-9]+)?\ \+([0-9]+)(,[0-9]+)?\ @@.* ]]; then
            line=${BASH_REMATCH[2]}
        elif [[ $REPLY =~ ^($esc\[[0-9;]+m)*([\ +-]) ]]; then
            REPLY=${REPLY:0:150}           # limit the line width, so it fits in a single line in most git log outputs
            if [[ "$path" == "/dev/null" ]]; then
                echo "File $previous_path deleted or moved."
                continue
            else
                echo "$path:$line: $REPLY"
            fi
            if [[ ${BASH_REMATCH[2]} != - ]]; then
                ((line++))
            fi
        fi
    done
}

###############################################################################

# main program loop: wait for changes and commit them
#   whenever inotifywait reports a change, we spawn a timer (sleep process) that gives the writing
#   process some time (in case there are a lot of changes or w/e); if there is already a timer
#   running when we receive an event, we kill it and start a new one; thus we only commit if there
#   have been no changes reported during a whole timeout period
eval "$INW" "${INW_ARGS[@]}" | while read -r line; do
    # is there already a timeout process running?
    if [[ -n "$SLEEP_PID" ]] && kill -0 $SLEEP_PID &>/dev/null; then
        # kill it and wait for completion
        kill $SLEEP_PID &>/dev/null || true
        wait $SLEEP_PID &>/dev/null || true
    fi

    # start timeout process
    (
        sleep "$SLEEP_TIME" # wait some more seconds to give apps time to write out all changes

        if [ -n "$DATE_FMT" ]; then
            FORMATTED_COMMITMSG="$(sed "s/%d/$(date "$DATE_FMT")/" <<< "$COMMITMSG")" # splice the formatted date-time into the commit message
        fi

        if [[ "$LISTCHANGES" -ge 0 ]]; then    # allow listing diffs in the commit log message, unless if there are too many lines changed
            DIFF_COMMITMSG="$($GIT diff -U0 $LISTCHANGES_COLOR | diff-lines)"
            LENGTH_DIFF_COMMITMSG=0
            if [[ "$LISTCHANGES" -ge 1 ]]; then
                LENGTH_DIFF_COMMITMSG=$(echo -n "$DIFF_COMMITMSG" | grep -c '^')
            fi
            if [[ "$LENGTH_DIFF_COMMITMSG" -le $LISTCHANGES ]]; then
                # Use git diff as the commit msg, unless if files were added or deleted but not modified
                if [ -n "$DIFF_COMMITMSG" ]; then
                    FORMATTED_COMMITMSG="$DIFF_COMMITMSG"
                else
                    FORMATTED_COMMITMSG="New files added: $($GIT status -s)"
                fi
            else
                #FORMATTED_COMMITMSG="Many lines were modified. $FORMATTED_COMMITMSG"
                FORMATTED_COMMITMSG=$($GIT diff --stat | grep '|')
            fi
        fi

        # CD into right dir
        cd "$TARGETDIR" || { stderr "Error: Can't change directory to '${TARGETDIR}'." ; exit 6; }
        STATUS=$($GIT status -s)
        if [ -n "$STATUS" ]; then # only commit if status shows tracked changes.
            $GIT add $GIT_ADD_ARGS # add file(s) to index
            $GIT commit $GIT_COMMIT_ARGS -m"$FORMATTED_COMMITMSG" # construct commit message and commit

            if [ -n "$PUSH_CMD" ]; then
                echo "Push command is $PUSH_CMD";
                eval $PUSH_CMD;
            fi
        fi
    ) & # and send into background

    SLEEP_PID=$! # and remember its PID
done