ui: add the possibility to returns None as username in ui
In a later patch we want to retrieve the current username or None if it isn't
defined. Add the acceptempty parameter instead of catching Abort.
# Files that just need to be migrated to the formatter.
# Do not add new files here!
contrib/chg/chg.c
contrib/chg/hgclient.c
contrib/chg/hgclient.h
contrib/chg/procutil.c
contrib/chg/procutil.h
contrib/chg/util.c
contrib/chg/util.h
contrib/hgsh/hgsh.c
mercurial/cext/base85.c
mercurial/cext/bdiff.c
mercurial/cext/charencode.c
mercurial/cext/charencode.h
mercurial/cext/diffhelpers.c
mercurial/cext/dirs.c
mercurial/cext/manifest.c
mercurial/cext/mpatch.c
mercurial/cext/osutil.c
mercurial/cext/parsers.c
mercurial/cext/pathencode.c
mercurial/cext/revlog.c
# Vendored code that we should never format:
contrib/python-zstandard/c-ext/bufferutil.c
contrib/python-zstandard/c-ext/compressiondict.c
contrib/python-zstandard/c-ext/compressionparams.c
contrib/python-zstandard/c-ext/compressionwriter.c
contrib/python-zstandard/c-ext/compressobj.c
contrib/python-zstandard/c-ext/compressor.c
contrib/python-zstandard/c-ext/compressoriterator.c
contrib/python-zstandard/c-ext/constants.c
contrib/python-zstandard/c-ext/decompressionwriter.c
contrib/python-zstandard/c-ext/decompressobj.c
contrib/python-zstandard/c-ext/decompressor.c
contrib/python-zstandard/c-ext/decompressoriterator.c
contrib/python-zstandard/c-ext/frameparams.c
contrib/python-zstandard/c-ext/python-zstandard.h
contrib/python-zstandard/zstd.c
contrib/python-zstandard/zstd/common/bitstream.h
contrib/python-zstandard/zstd/common/entropy_common.c
contrib/python-zstandard/zstd/common/error_private.c
contrib/python-zstandard/zstd/common/error_private.h
contrib/python-zstandard/zstd/common/fse.h
contrib/python-zstandard/zstd/common/fse_decompress.c
contrib/python-zstandard/zstd/common/huf.h
contrib/python-zstandard/zstd/common/mem.h
contrib/python-zstandard/zstd/common/pool.c
contrib/python-zstandard/zstd/common/pool.h
contrib/python-zstandard/zstd/common/threading.c
contrib/python-zstandard/zstd/common/threading.h
contrib/python-zstandard/zstd/common/xxhash.c
contrib/python-zstandard/zstd/common/xxhash.h
contrib/python-zstandard/zstd/common/zstd_common.c
contrib/python-zstandard/zstd/common/zstd_errors.h
contrib/python-zstandard/zstd/common/zstd_internal.h
contrib/python-zstandard/zstd/compress/fse_compress.c
contrib/python-zstandard/zstd/compress/huf_compress.c
contrib/python-zstandard/zstd/compress/zstd_compress.c
contrib/python-zstandard/zstd/compress/zstd_opt.h
contrib/python-zstandard/zstd/compress/zstdmt_compress.c
contrib/python-zstandard/zstd/compress/zstdmt_compress.h
contrib/python-zstandard/zstd/decompress/huf_decompress.c
contrib/python-zstandard/zstd/decompress/zstd_decompress.c
contrib/python-zstandard/zstd/dictBuilder/cover.c
contrib/python-zstandard/zstd/dictBuilder/divsufsort.c
contrib/python-zstandard/zstd/dictBuilder/divsufsort.h
contrib/python-zstandard/zstd/dictBuilder/zdict.c
contrib/python-zstandard/zstd/dictBuilder/zdict.h
contrib/python-zstandard/zstd/zstd.h
hgext/fsmonitor/pywatchman/bser.c