Should lilac do a clean up after `makepkg -od`?

I encountered a problem yesterday that the moe lilac sent me a e-mail to remind me the that vim-youcompleteme-git was failed to build AGAIN! The error occured while runing makepkg -od.

I did a research and found it was mainly due to the existing of the old $srcdir generated by last runing of makepkg -od, and a patch was applied twice:

==> 正在开始 prepare()...
  -> Setting up Git submodules...
patching file YouCompleteMe/autoload/youcompleteme.vim
patching file ycmd/default_settings.json
Reversed (or previously applied) patch detected!  Skipping patch.
1 out of 1 hunk ignored -- saving rejects to file ycmd/default_settings.json.rej
==> 错误： 在 prepare() 中发生一个错误。
    正在放弃...

Since the file to be patched is actually in a git submodule, It keeps patched (but not reset to the origin one at the process of extracting sources) at the second time makepkg -od running. The submodule in PKGBUILD is initialized as the wiki says.

I think about some solutions, but don't know which is best:

Force clean up the submodule dircetories before git submodule init in PKGBUILD. However, this is unnacessary in most cases and may make PKGBUILD a little bit confusing.
Clean up the $srcdir (or more specifically, remove it) in lilac.py. However, due to the different setting of BUILDDIR in ~/.makepkg.conf or /etc/makepkg.conf, it is not easy to obtain the location where the $srcdir is.
Use makepkg -od --noprepare here. This is a bit tricky and since pkgver() is executed after prepare(), pkgver may be wrongly acquired by lilac due to the skip of prepare().
Use makepkg -odc at the line mentioned above. This force makepkg remove the $srcdir after obtaining the sources and running pkgver() to update PKGBUILD. (I prefer this)

So, which one is preferable?

archlinuxcn / lilac

Should lilac do a clean up after `makepkg -od`? #39