stream-clone: bail-out earlier if pull is partial
The `canperformstreamclone` function is bit messy. However it seems clearer to
me to process the very generic condition about "can we consider a stream-clone
at all", before checking if a stream-clone is requested and if a compatible
protocol can be negotiated with the server.
So I am doing some gratuitous movement so reorder conditional.
# Files that just need to be migrated to the formatter.
# Do not add new files here!
mercurial/cext/manifest.c
mercurial/cext/osutil.c
# Vendored code that we should never format:
syntax: glob
contrib/python-zstandard/**.c
contrib/python-zstandard/**.h
hgext/fsmonitor/pywatchman/**.c
mercurial/thirdparty/**.c
mercurial/thirdparty/**.h
mercurial/pythoncapi_compat.h