rebase: fix path auditing to audit path relative to repo root (issue5818)
Before this patch, when rebasing a file called "foo/bar", we would
check e.g. if "/foo" (i.e. rooted at the file system root) was a
symlink.
Differential Revision: https://phab.mercurial-scm.org/D5361
$ 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