git: How to split off library from project? filter-branch, subtree?

Question

So, I\'ve a bigger (closed source) project, and in the context of this project created a library which could also be useful elsewhere, I think.

I now want to split o

Answer 1

I've done something similar, but splitting several dirs of stuff into an entirely separate repo on an encrypted partition (/secure/tmp/newrepo), so they were not available to a laptop thief. I wrote the shell script and then did: git filter-branch --tree-filter '~/bin/tryit /secure/tmp/newrepo personal private' -- 95768021ff00216855868d12556137115b2789610..HEAD (the SHA avoids commits before either directory came into existance)

---

#!/bin/sh
# to be used with  e.g:
# git filter-branch --tree-filter '~/bin/tryit /secure/tmp/newrepo personal private' 
# Don't do it on any repository you can't repeatedly do: 
#   rm -rf foo ; git clone /wherever/is/foo 
# when it breaks
SRC=`pwd`
DEST=$1
shift
MSG=/dev/shm/msg.txt
TAR=/dev/shm/tmp.tar
LIST=/dev/shm/list.txt
LOG=/dev/shm/log
DONE=''

echo $GIT_AUTHOR_DATE >> $LOG
git show --raw $GIT_COMMIT > $MSG 

for A in $* 
do 

if [ -d $A ] 
then 
DONE=${DONE}x
tar -cf $TAR $A 
tar -tf $TAR > ${LIST}
cat ${LIST} >> ${LOG}
rm -rf ${A}
cd ${DEST}
tar -xf $TAR
else
echo $A non-existant >> ${LOG}
fi
cd $SRC
done

if [ -z "${DONE}" ]
then
echo Empty >>$LOG
else
cd ${DEST}
unset GIT_INDEX_FILE
unset GIT_DIR
unset GIT_COMMIT
unset GIT_WORK_TREE
touch foo
git add .
git commit -a -F ${MSG}  >> ${LOG}
fi
exit 0

---

For your purposes you'd probably want to have a different spec for the tar (e.g. --exclude= ) and then use cat ${LIST} | xargs rm to only remove stuff in the tar, but getting that right is not too tricky, I hope.

The unset stuff and exit 0 are important, since filter-branch sets those to your source repo (not what you want!) and will die if sh passes on a non-zero exit code from the last command in your script.