svn-to-monorepo

#!/bin/bash
__SUMMARY__=$(cat <<"__TLDR__"
svn-to-monorepo

Converts the VDT SVN repo to a Git repo with a 'monorepo' layout --
meaning all of the branches are in a directory, instead of there being
one Git branch per SVN branch.
__TLDR__
)

AUTHORS_FILE=.svn-authors.txt
AUTHORS_URL=https://vdt.cs.wisc.edu/svn-authors.txt
GITHUB_REPOSITORY=osg-htc/software-packaging
SVN=https://vdt.cs.wisc.edu/svn

PROG=${0##*/}
PROGDIR=$(dirname "$0")

FILTER_SCRIPT=$PROGDIR/svn-to-monorepo-filter-monorepo

ask_yn () {
    echo >&2 "$@"
    while read -r; do
        case $REPLY in
            [Yy]*) return 0;;
            [Nn]*) return 1;;
            *) echo >&2 "Enter yes or no";;
        esac
    done
    return 2  # EOF
}

eecho () {
    echo >&2 "$@"
}

fail () {
    set +exu
    ret=${1:-1}
    shift &>/dev/null || :
    if [[ -z $* ]]; then
        echo "$PROG: unspecified failure, exiting" >&2
    else
        echo "$PROG:" "$@" >&2
    fi
    exit "$ret"
}

usage () {
    echo >&2 "$__SUMMARY__"
    echo >&2
    echo >&2 "Usage: $PROG <destination>"
    exit "$1"
}

require_program () {
    command -v "$1" &>/dev/null ||
        fail 127 "Required program '$1' not found in PATH"
}

GIT () {
    git -C "$DESTDIR" "$@"
}

GIT_RAW () {
    git -C "$DESTDIR_RAW" "$@"
}


#
# Parse args
#

if [[ $1 == -h || $1 == --help ]]; then
    usage 0
fi
if [[ $# != 1 ]]; then
    usage 2
fi
DESTDIR=$(readlink -f "$1")
DESTDIR_RAW=${DESTDIR}.raw


set -o nounset

#
# Check for required programs
#

require_program git
git svn -h >/dev/null || fail 127 "git svn not available; try installing the git-svn package (or equivalent on your distribution)"
require_program curl
require_program git-filter-repo
[[ -x $FILTER_SCRIPT ]] || fail 127 "$FILTER_SCRIPT not found or not executable"

#
# Create a fresh dir for the Git repo
#
if [[ -d $DESTDIR ]]; then
    if ask_yn "$DESTDIR already exists. Replace it?"; then
        rm -rf "${DESTDIR}.bak" || fail 4 "Unable to delete ${DESTDIR}.bak"
        mv  -f "${DESTDIR}" "${DESTDIR}.bak" || fail 4 "Unable to move ${DESTDIR} out of the way"
    else
        fail 4 "Not replacing $DESTDIR"
    fi
else
    mkdir "$DESTDIR" || fail 5 "Could not create $DESTDIR"
fi

#
# Init the repo
#

if [[ ! -e $DESTDIR_RAW/.git/svn ]]; then
    if [[ -e $DESTDIR_RAW ]]; then
        if ask_yn "$DESTDIR_RAW already exists but does not look like a git-svn repo. Delete it?"; then
            rm -rf "$DESTDIR_RAW" || fail 4 "Unable to delete $DESTDIR_RAW"
        else
            fail 4 "Not deleting $DESTDIR_RAW"
        fi
    fi
    mkdir "$DESTDIR_RAW" || fail 5 "Could not create $DESTDIR_RAW"
    GIT_RAW svn init $SVN/native/redhat --ignore-paths='^(tags)|(/_[a-z_]+/|[.]tar[.]gz$|[.]rpm$)'  || fail 6 "Error creating Git repo"
    curl -o "$DESTDIR_RAW/.git/$AUTHORS_FILE" "$AUTHORS_URL" || fail 7 "Could not download authors file"
    GIT_RAW config svn.authorsfile ".git/$AUTHORS_FILE"

    #
    # Fetch from SVN and filter the results
    #

    eecho "*"
    eecho "* Fetching SVN commits for the first time, go make a sandwich"
    eecho "*"
    GIT_RAW svn fetch -q --log-window=1000  ||  fail 7 "Fetch failed"
else
    eecho "*"
    eecho "* Updating SVN commits"
    eecho "*"
    GIT_RAW svn rebase  ||  fail 7 "Rebase failed"
fi

eecho "*"
eecho "* Cloning and filtering"
eecho "*"
git clone --no-local "$DESTDIR_RAW" "$DESTDIR" || fail 11 "clone from $DESTDIR_RAW to $DESTDIR failed"
"$FILTER_SCRIPT" "$DESTDIR"  ||  fail 8 "Filter failed"

#
# Configure the remote and fetch from it
#
GIT remote add github https://github.com/${GITHUB_REPOSITORY}  ||  fail 9 "Adding GitHub as a remote failed"
timeout 180 git -C "$DESTDIR" fetch github  ||  fail 11 "Fetch from GitHub failed"
GIT branch --set-upstream-to=github/main

#
# Done!  Push if we can do it without rewriting history.
#
eecho "*"
eecho "* Repo conversion complete"
eecho "*"

if GIT merge-base --is-ancestor github/main main
then
    eecho "* Resulting repo is a fast-forward"
    if ask_yn "Push to GitHub?"; then
        eecho "* Pushing"
        GIT push github main  ||  fail 10 "Failed to push"
        eecho "* Done"
    else
        eecho "* Not pushing, as requested. Done."
        exit 0
    fi
else
    eecho "* New conversion is not a fast forward; please investigate"
fi


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