merge-patches script : needs to output a git-moved file after continue

[estellecomment]

After fixing a conflict in a patch, you run bash ./scripts/tchap/merge-patches.sh continue
It creates the patch file, but you still need to do a lot of moving files around, and making git understand that the patch file has been renamed.

What we want is something like this :

[estellecomment]

Currently to fix I have to do this :

mv patches/cross-signing-ui/matrix-react-sdk+3.81.0.patch matrix-react-sdk+3.81.0.patch
cp patches/cross-signing-ui/matrix-react-sdk+3.79.0.patch patches/cross-signing-ui/matrix-react-sdk+3.79.0.old.patch
git mv patches/cross-signing-ui/matrix-react-sdk+3.79.0.patch patches/cross-signing-ui/matrix-react-sdk+3.81.0.patch
mv matrix-react-sdk+3.81.0.patch patches/cross-signing-ui/matrix-react-sdk+3.81.0.patch
git add patches/cross-signing-ui/matrix-react-sdk+3.81.0.patch

[estellecomment]

started something in #766 , not clean enough yet (crashes as soon as something is unexpected, and some vars are hardcoded)