logexchange: convert paths to unix when detecting the active path
This fixes the problem in the tests[1] where Windows was showing the whole path
as the remotename for local repositories.
Somebody with a better understanding of this extension should probably take a
deeper look. There may be other cases that need to be converted- specifically
the `elif not instance` and the missing `else` cases in activepath(). I also
noticed when adding debug prints that the absolute path is stored in the file,
probably not normalized. (It's wrapped up in $TESTTMP.)
[1] https://buildbot.mercurial-scm.org/builders/Win7%20x86_64%20hg%20tests/builds/1042/steps/run-tests.py%20%28python%202.7.13%29/logs/stdio
$ hg init
$ "$PYTHON" -c 'open("a", "wb").write(b"confuse str.splitlines\nembedded\rnewline\n")'
$ hg ci -Ama -d '1 0'
adding a
$ echo clean diff >> a
$ hg ci -mb -d '2 0'
$ hg diff -r0 -r1
diff -r 107ba6f817b5 -r 310ce7989cdc a
--- a/a Thu Jan 01 00:00:01 1970 +0000
+++ b/a Thu Jan 01 00:00:02 1970 +0000
@@ -1,2 +1,3 @@
confuse str.splitlines
embedded\r (no-eol) (esc)
newline
+clean diff