git-fix-date

#!/usr/bin/env bash
##############################################################################
#
# git-fix-date
# -------------------
# Change all occurences of one timezone in git commits to another.
#
# @author Isis Agora Lovecruft, 0x2cdb8b35
# @date 24 March 2013
# @version 0.0.1
##############################################################################

## git filter-branch to replace GIT_AUTHOR_DATE and GIT_COMMITTER_DATE, setting
## all times to their equivalent in UTC.

## The path to your copy of my gitdate script:
GITDATE=`which gitdate`

if test -z "$DONT_CARE_IF_ITS_BROKEN" ; then
    printf "\nThis script is broken. Please fix me!\n\nIt currently needs:\n"
    printf "  * A way to run git-filter-branch in a coproc, taking the function filterdate()\n"
    printf "    (included in this script), or the contents of it, as an argument to either\n"
    printf "    '--env-filter' or '--commit-filter'.\n"
    printf "  * A way to cause the '$@' variables in filterdate() to not apply to the cmdline\n"
    printf "    arguments for this file, but to the commit hashes iterated through \n"
    printf "    filterdate(). I think this would be something like 'set -e -' combined with\n"
    printf "     git-filter-branch's internal map() function, but I'm not sure.\n"
    printf "  * The thing I was trying to do with coproc will not work because coprocesses\n"
    printf "    in bash are not designed as usual, and will not handle loops. \n"
    printf "    see https://stackoverflow.com/q/7689100 https://stackoverflow.com/q/7682196 \n\n"
    exit 1
fi

skip_commit()
{
    shift;
    while [ -n "$1" ];
    do
        shift;
        map "$1";
        shift;
    done;
}

function filterdate () 
{
    if [ "${GIT_AUTHOR_DATE: -5}" = "$orig_tz" ] ; then 
        . /home/isis/scripts/gitdate "$GIT_AUTHOR_DATE"
        export GIT_AUTHOR_DATE
        git commit-tree "$@"
    else 
        skip_commit "$@"
    fi
}

cat <<EOF
Which timezone would you like to change to UTC? (e.g. if "git log"
shows "AuthorDate: Sun Aug 19 08:34:12 2012 -0400", then the timezone
should be specified as the offset, e.g. "-0400":
EOF

read -p"What is the offset of the timezone you would like to filter? " orig_tz
echo "Should we filter the current branch now, changing all occurences of"
read -p"the original timezone $orig_tz to UTC +0000? (y/N) " choice
read -p"Should we also modify the git AuthorDate timestamps to be UTC? (y/N) " modauth

case $choice in
    y|Y)
        case $modauth in
            y|Y)
                git filter-branch --commit-filter '
                    if [ "${GIT_AUTHOR_DATE: -5}" = "$orig_tz" ] ; then 
                        . $GITDATE "$GIT_AUTHOR_DATE" ; 
                        git commit-tree "$@" ;
                    else
                        skip_commit "$@" ;
                    fi' HEAD
                ;;
            * )
                set -x --
                read GAD GCD < <(git filter-branch --commit-filter '
                         if [ "${GIT_AUTHOR_DATE: -5}" = "$orig_tz" ] ; then
                             . $GITDATE "$GIT_AUTHOR_DATE" ;
                             git commit-tree '$@' ;
                         else
                             skip_commit '$@' ;
                         fi ' HEAD)
                echo $GAD
                echo $GCD

                # { coproc { git filter-branch --commit-filter '
                #          if [ "${GIT_AUTHOR_DATE: -5}" = "$orig_tz" ] ; then
                #              . $GITDATE "$GIT_AUTHOR_DATE" ;
                #              git commit-tree $@ ;
                #          else
                #              skip_commit $@ ;
                #          fi ' HEAD ;} >&3 ;} 3>&1

                #exec >&${fdate[0]}
                #while IFS= read -ru 3 x; do 
                #    printf '%s\n' "$x" 1>&0
                #done
                ;;
            esac
        ;;
    *)
        echo "Exiting..." && exit 0
        ;;
esac