util: implement `writelines()` on atomictempfile With typehints on the vfs objects, pytype will flag this: FAILED: /mnt/c/Users/Matt/hg/.pytype/pyi/mercurial/patch.pyi /usr/bin/python3.8 -m pytype.single --imports_info /mnt/c/Users/Matt/hg/.pytype/imports/mercurial.patch.imports --module-name mercurial.patch -V 3.7 -o /mnt/c/Users/Matt/hg/.pytype/pyi/mercurial/patch.pyi --analyze-annotated --nofail --quick /mnt/c/Users/Matt/hg/mercurial/patch.py File "/mnt/c/Users/Matt/hg/mercurial/patch.py", line 535, in writerej: No attribute 'writelines' on mercurial.util.atomictempfile [attribute-error] In Union[ mercurial.util.atomictempfile, mercurial.vfs.checkambigatclosing, mercurial.vfs.delayclosedfile, mercurial.windows.fdproxy, mercurial.windows.mixedfilemodewrapper ] It's not a real problem there (atomictempfile is only created by passing different args), but it's reasonable for this to implement the function and behave like a normal file. There are other functions missing that can be added if/when needed.