Git Diffgen

mergelog.txt

#!/bin/sh

#------------------------------------------------------------------------------#

MERGE="no"
CHECK_ONLY="no"
PROGNAME=`echo "$0" | sed 's@.*/@@g'`

#------------------------------------------------------------------------------#

USAGE="Usage: $PROGNAME [-m] [-c] [-b BRANCH] GITDIR"

HELP_MSG="
Unconditionally update a repo to match the remote. Generate a changelog.
$USAGE

Options:
    -b BRANCH, Manually specify the remote's branch.

    -c,        Check for updates, but take no other action. Exit success
               the repo is up-to-date.

    -m,        Merge the remote after fetching.

    -h,        Print this message and exit.
"

usage() {
    local exit_code="$1"
    local stream="1"

    if [ "$exit_code" = "" ]; then
        stream="2"
        exit_code=0
    fi

    printf "$USAGE\n" >&$stream
    exit $exit_code
}

help() {
    local exit_code="$1"
    local stream="1"

    if [ "$exit_code" = "" ]; then
        stream="2"
        exit_code=0
    fi

    printf "$HELP_MSG\n" >&$stream
    exit $exit_code
}

#------------------------------------------------------------------------------#

for arg in $@; do
    if [ "$arg" = "--help" ]; then
        help
    fi
done

while getopts "mchb:" name $ARGS 2>/dev/null
do
    case $name in
        b) BRANCH="$OPTARG";;
        m) MERGE="yes";;
        c) CHECK_ONLY="yes";;
        h) help;;
        *) usage 1;;
    esac
done

shift "$(($OPTIND-1))"
GITDIR="$1"
shift

if [ "$*" != "" ]; then
    usage 1
fi

#------------------------------------------------------------------------------#

if [ "x$GITDIR" = "x" ]; then
    usage 1
fi

if [ "x$BRANCH" = "x" ]; then
    BRANCH=`git -C "$GITDIR" branch | grep -oP '(?<=[*] )[^(].*'`
fi

if [ "x$BRANCH" = "x" ]; then
    echo "Error: couldn't guess branch of $GITDIR. Please specify with -b." >&2
    exit 1
fi

#------------------------------------------------------------------------------#

in_set() {
    # Succeeds if $query is in $set, and fails otherwise.

    local set="$1"
    local query="$2"
    local item=""

    for item in $set; do
        if [ "$item" = "$query" ]; then
            return 0
        fi
    done

    return 1
}

difference() {
    # Returns set_a - set_b.

    local set_a="$1"
    local set_b="$2"
    local result=""
    local item=""

    for item in $set_a; do
        if ! in_set "$set_b" "$item"; then
            result="$result $item"
        fi
    done

    echo "`echo $result`"
}

#------------------------------------------------------------------------------#

git -C "$GITDIR" fetch -f origin "$BRANCH" 1>/dev/null 2>&1

#------------------------------------------------------------------------------#

CURRENT="`git -C "$GITDIR" rev-parse HEAD`"
TARGET="`git -C "$GITDIR" rev-parse "origin/$BRANCH"`"

if [ "$CHECK_ONLY" = "yes" ]; then
    if [ "$CURRENT" = "$TARGET" ]; then
        exit 0
    fi
    exit 1
fi

#------------------------------------------------------------------------------#

BOTTOM="`git -C "$GITDIR" merge-base $CURRENT origin/$BRANCH`"

OLD_COMMITS=$(git -C "$GITDIR" log --pretty=format:"%H" $BOTTOM...$CURRENT)
NEW_COMMITS=$(git -C "$GITDIR" log --pretty=format:"%H" $BOTTOM...$TARGET)

TO_DELETE=`difference "$OLD_COMMITS" "$NEW_COMMITS"`
TO_ADD=`difference "$NEW_COMMITS" "$OLD_COMMITS"`

#------------------------------------------------------------------------------#

for record in $TO_ADD; do
    git -C "$GITDIR" show -s $record --pretty=format:"+%h: %s" | cat
    printf "\n"
done

for record in $TO_DELETE; do
    git -C "$GITDIR" show -s $record --pretty=format:"-%h: %s" | cat
    printf "\n"
done

#------------------------------------------------------------------------------#

if [ "$MERGE" != "yes" ]; then
    exit 0
fi

git -C "$GITDIR" checkout origin/$BRANCH 1>/dev/null
git -C "$GITDIR" branch -m $BRANCH __old_$BRANCH 1>/dev/null
git -C "$GITDIR" branch $BRANCH 1>/dev/null
git -C "$GITDIR" checkout $BRANCH 1>/dev/null
git -C "$GITDIR" branch -D __old_$BRANCH 1>/dev/null
git -C "$GITDIR" branch -u origin/$BRANCH $BRANCH 1>/dev/null