dirstate: prevent useless util.fspath() invocation for '.'
at first of dirstate.walk() on case insensitive filesystem,
normalization of '.' causes util.fspath() invocation, but '.' is not
cached in it.
this invocation is not only useless, but also harmful: initial "hg
tag" causes creation of ".hgtags" file after dirstate.walk(), and
looking up ".hgtags" in cache will fail, because directory contents of
root is already cached at util.fspath() invocation for '.'.
$ unset HGUSER
$ EMAIL="My Name <myname@example.com>"
$ export EMAIL
$ hg init test
$ cd test
$ touch asdf
$ hg add asdf
$ hg commit -m commit-1
$ hg tip
changeset: 0:53f268a58230
tag: tip
user: My Name <myname@example.com>
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ unset EMAIL
$ echo 1234 > asdf
$ hg commit -u "foo@bar.com" -m commit-1
$ hg tip
changeset: 1:3871b2a9e9bf
tag: tip
user: foo@bar.com
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ echo "[ui]" >> .hg/hgrc
$ echo "username = foobar <foo@bar.com>" >> .hg/hgrc
$ echo 12 > asdf
$ hg commit -m commit-1
$ hg tip
changeset: 2:8eeac6695c1c
tag: tip
user: foobar <foo@bar.com>
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ echo 1 > asdf
$ hg commit -u "foo@bar.com" -m commit-1
$ hg tip
changeset: 3:957606a725e4
tag: tip
user: foo@bar.com
date: Thu Jan 01 00:00:00 1970 +0000
summary: commit-1
$ echo 123 > asdf
$ echo "[ui]" > .hg/hgrc
$ echo "username = " >> .hg/hgrc
$ hg commit -m commit-1
abort: no username supplied (see "hg help config")
[255]
$ rm .hg/hgrc
$ hg commit -m commit-1 2>&1
No username found, using '[^']*' instead (re)
$ echo space > asdf
$ hg commit -u ' ' -m commit-1
transaction abort!
rollback completed
abort: empty username!
[255]