#!/bin/bash

# Convert an SVN dumpfile into a Git repository.  (Note: an
# "SVN dumpfile" is a file created with 'svnadmin dump'.)
#
# ###########################################################
# ####                                                  ##### 
# ####  HEY, INSTEAD OF USING THIS SCRIPT, JUST USE     #####
# ####  JOHN ALBIN'S 'git-svn-migrate' SCRIPTS, AT:     #####
# ####                                                  #####
# ####    https://john.albin.net/git/git-svn-migrate    #####
# ####    https://github.com/JohnAlbin/git-svn-migrate  #####
# ####                                                  #####
# ####  HE'S ALREADY SOLVED EVERYTHING.  JUST USE HIS.  #####
# ####                                                  ##### 
# ###########################################################
#
# This script isn't even fully working yet, due to an unfixed
# bug;  search for "TODO: THIS IS WHERE THE PROBLEM IS" below
# for details.
#
# ###########################################################
# 
# This requires the 'git-svn' package to be installed.  If you don't
# know whether you have it or not, run the command 'git svn help'.  If
# you get some help output, then all is good.  If you don't, then do
# 'sudo apt-get install git-svn' (on Debian-flavored systems).
#
# Usage:
# 
#   $ ./svndump2git foo.dump
#   
# That produces Git repository 'git-foo-repos'.  Or it would, if it
# weren't for the above-mentioned bug.  I was writing this to help
# Leonard Richardson with some repository conversions, with guidance
# from https://john.albin.net/git/convert-subversion-to-git/, and then
# Leonard and I discovered that at the end of that blog post the the
# author links to https://john.albin.net/git/git-svn-migrate, where
# he's scripted everything up.

# License: Let's say GNU GPL v3 for now.  But again, don't use this,
# because it's not ready.  Use John Albin's git-svn-migrate scripts.

# Historically this is "master", but lately there has been momentum
# towards "main" instead, which is why this is adjustable here.
GIT_DEFAULT_BRANCH_NAME="master"

if [ -z "${1}" ]; then
  echo "ERROR: SVN dumpfile argument required; should end with \".dump\"" >&2
  exit 1
fi

SVN_DUMPFILE="${1}"
REPOS_BASENAME=`basename "${1}" .dump`

if [ "${SVN_DUMPFILE}" = "${REPOS_BASENAME}" ]; then
  echo "ERROR: SVN dumpfile name must end with \".dump\"" >&2
  exit 1
fi

SVN_REPOS_PATH=svn-"${REPOS_BASENAME}-repos"
SVN_REPOS_URL="file://`pwd`/${SVN_REPOS_PATH}"
GIT_REPOS_PATH=git-"${REPOS_BASENAME}-repos"
AUTHORS_TRANSFORM_FILE="${REPOS_BASENAME}"-authors-transform.txt

# Make sure neither repository exists yet.
SOMETHING_IS_IN_THE_WAY="no"
if [ -f "${SVN_REPOS_PATH}" -o -d "${SVN_REPOS_PATH}" ]; then
  echo "'${SVN_REPOS_PATH}' exists.  Please move it out of the way." >&2
  SOMETHING_IS_IN_THE_WAY="yes"
fi
if [ -f "${GIT_REPOS_PATH}" -o -d "${GIT_REPOS_PATH}" ]; then
  echo "'${GIT_REPOS_PATH}' exists.  Please move it out of the way." >&2
  SOMETHING_IS_IN_THE_WAY="yes"
fi
if [ "${SOMETHING_IS_IN_THE_WAY}" != "no" ]; then
  exit 1
fi

svnadmin create "${SVN_REPOS_PATH}"

# You could add '--quiet' here to suppress the noisy
# revision-by-revision progress output. 
svnadmin load "${SVN_REPOS_PATH}" < "${SVN_DUMPFILE}"

# Create the authors-transform file.
svn log -q "${SVN_REPOS_URL}" \
  | awk -F '|' '/^r/ {sub("^ ", "", $2); sub(" $", "", $2); print $2" = "$2" <"$2">"}' \
  | sort -u \
  > ${AUTHORS_TRANSFORM_FILE}

echo ""
echo "Now I will pause while you edit \"${AUTHORS_TRANSFORM_FILE}\""
echo "to supply real names and email addresses for as many of the committers"
echo "as you can.  After you're done, press Return to continue the conversion."
echo ""
read

# Start by creating a non-bare temporary Git repository, in which we will
# set up .gitignore based on svn:ignore properties.
rm -rf "${GIT_REPOS_PATH}-tmp"
git svn clone "${SVN_REPOS_URL}" --no-metadata -A "${AUTHORS_TRANSFORM_FILE}" --stdlayout "${GIT_REPOS_PATH}-tmp"
# Now set up the ignores.
#
# ##### TODO: THIS IS WHERE THE PROBLEM IS #####
#
# The command 'git svn show-ignore > .gitignore' below produces an
# error:
#
#   config --get svn-remote.svn.fetch :refs/remotes/git-svn$: command returned error: 1
#
# I don't know the cause, and as of 2020-06-24 haven't debugged it,
# because then Leonard and I discovered that John Albin had scripted
# this all already, so why are you even here?  Just go use John's.
(cd "${GIT_REPOS_PATH}-tmp"; \
 git svn show-ignore > .gitignore; \
 git add .gitignore; \
 git commit -m 'Convert svn:ignore properties to .gitignore.'; \
)

# Create the *real* repository, as a bare repository, and
# set its default branch to match SVN's "trunk" branch name.
git init --bare ${GIT_REPOS_PATH}
(cd ${GIT_REPOS_PATH}; \
 git symbolic-ref HEAD "refs/heads/trunk"; \
)

# Push everything from the tmp repository to the real one.
(cd "${GIT_REPOS_PATH}-tmp"; \
 git remote add bare "../${GIT_REPOS_PATH}"; \
 git config remote.bare.push 'refs/remotes/*:refs/heads/*'; \
 git push bare; \
)

# We're done with the tmp repository.
rm -rf "${GIT_REPOS_PATH}-tmp"

# Rename trunk to the Git default branch name.
(cd "${GIT_REPOS_PATH}"; \
 git branch -m trunk "${GIT_DEFAULT_BRANCH_NAME}"; \
)

# This part is totally untested.
cd "${GIT_REPOS_PATH}"
git for-each-ref --format='%(refname)' refs/heads/tags | cut -d / -f 4 |
while read ref
do
  git tag "$ref" "refs/heads/tags/$ref";
  git branch -D "tags/$ref";
done
cd ..