Migrating from SVN

Migrating from SVN#

Note

This section should only be relevant until the 2.x release at which point the SVN repository shall be completely removed.

The basic idea is to use git svn[1], following the standard git book approach.

Getting the SVN sources#

For the first part we don’t need every commit, so a checkout will work over clone.

svn co https://theory.cm.utexas.edu/svn/eon eonSVNonly

We will use this to determine author information.

cd eonSVNonly
svn log > loggy
svn log --xml --quiet | grep author | sort -u | \
  perl -pe 's/.*>(.*?)<.*/$1 = /' > ../authors.txt

Now, the authors.txt file can be edited to map to existing GitHub users. It is also useful to grab the loggy file to try to timestamp when each user was active.

Importing history#

With these in hand, we can now actually import the svn history[2] via:

mkdir eon_svn && cd eon_svn
git svn init https://theory.cm.utexas.edu/svn/eon --no-metadata --prefix ""
git config svn.authorsfile ../authors.txt
git svn fetch

This will take much longer, since fetch, unlike checkout downloads all changes. Cross-reference with the “fuller” variant from here:

svn log | awk -F '|' '/^r/ {sub("^ ", "", $2); 
sub(" $", "", $2); print $2" = "$2" <"$2">"}' | sort -u > authors-transform.txt
# Includes things like
(no author) = (no author) <na@NODATA>

By project convention, if the command fails with an author not defined use username = username <username@NODATA>, then retry the git svn fetch.

Also note that it is by far preferably to use Github handles for email addresses, <haozeke@users.noreply.github.com> to reduce leaking personally identifiable information.

Merging upstream#

Since the SVN source has no tags or branches, there are no cleanup tasks required.

Note

eON used to use CVS for managing history, which was not imported when the switch to SVN took place, so rememeber to rebase a dummy commit co-authored by contributors before 2010!

Since we already have svn as a branch and even tags, it is a bit of a pain to take updates. Essentially we will have to rebase onto the “new” commits.

git branch -d main # extraneous
git checkout -b svn_new
git remote add origin git@github.com:TheochemUI/eongit
git pull
# Add in the commits from the older svn branch
# Just the gitignore bits
git cherry-pick b8794c316882b09e6421a3ba9f707a893accb636
git cherry-pick 35ea1448ee8707e06d4b314fbdfb0fabe859a206

Now we are ready to cut and push a new tag.

git checkout svn_new
git checkout -b main_tk3
git reset --hard $LAST_TAG_COMMIT # July 1 this is 0e263123
# from to
git rebase --ignore-whitespace --rebase-merges --onto main_tk3 b8794c3^ 5505ae2
# After fixing many changes 594826a
git branch main_fin
git push -u origin main_fin
# Adding back the newer commits after the reset
git rebase --ignore-whitespace --rebase-merges --onto main_fin 0e26312^ c267e1c
git push origin HEAD:main_fin

Note that the ignore-whitespace option might be problematic for Python changes, but for C++ only changesets it should be fine.

Documentation only commits are ported separately, and skipped during the rebase, since these will be in files “deleted by us”.

# Open next both merged
emacsclient -n $(git diff --name-only --diff-filter=U | head -n 1)

Note

Remember to diff the folders (e.g. via meld) after this operation, and confirm only expected changes are present.

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