posix: give checklink a fast path that cache the check file and is read only
util.checklink would create a symlink and remove it again. That would sometimes
happen multiple times. Write operations are relatively expensive and give disk
tear and noise for applications monitoring file system activity.
Instead of creating a symlink and deleting it again, just create it once and
leave it in .hg/cache/check-link . If the file exists, just verify that
os.islink reports true. We will assume that this check is as good as symlink
creation not failing.
Note: The symlink left in .hg/cache has to resolve to a file - otherwise 'make
dist' will fail ...
test-symlink-os-yes-fs-no.py does some monkey patching to simulate a platform
without symlink support. The slightly different testing method requires
additional monkeying.
#require symlink
$ echo "[extensions]" >> $HGRCPATH
$ echo "mq=" >> $HGRCPATH
$ hg init
$ hg qinit
$ hg qnew base.patch
$ echo aaa > a
$ echo bbb > b
$ echo ccc > c
$ hg add a b c
$ hg qrefresh
$ readlink.py a
a -> a not a symlink
test replacing a file with a symlink
$ hg qnew symlink.patch
$ rm a
$ ln -s b a
$ hg qrefresh --git
$ readlink.py a
a -> b
$ hg qpop
popping symlink.patch
now at: base.patch
$ hg qpush
applying symlink.patch
now at: symlink.patch
$ readlink.py a
a -> b
test updating a symlink
$ rm a
$ ln -s c a
$ hg qnew --git -f updatelink
$ readlink.py a
a -> c
$ hg qpop
popping updatelink
now at: symlink.patch
$ hg qpush --debug
applying updatelink
patching file a
committing files:
a
committing manifest
committing changelog
now at: updatelink
$ readlink.py a
a -> c
$ hg st
test replacing a symlink with a file
$ ln -s c s
$ hg add s
$ hg qnew --git -f addlink
$ rm s
$ echo sss > s
$ hg qnew --git -f replacelinkwithfile
$ hg qpop
popping replacelinkwithfile
now at: addlink
$ hg qpush
applying replacelinkwithfile
now at: replacelinkwithfile
$ cat s
sss
$ hg st
test symlink removal
$ hg qnew removesl.patch
$ hg rm a
$ hg qrefresh --git
$ hg qpop
popping removesl.patch
now at: replacelinkwithfile
$ hg qpush
applying removesl.patch
now at: removesl.patch
$ hg st -c
C b
C c
C s
replace broken symlink with another broken symlink
$ ln -s linka linka
$ hg add linka
$ hg qnew link
$ hg mv linka linkb
$ rm linkb
$ ln -s linkb linkb
$ hg qnew movelink
$ hg qpop
popping movelink
now at: link
$ hg qpush
applying movelink
now at: movelink
$ readlink.py linkb
linkb -> linkb