rust-dirstate: call rust dirstatemap from Python
Since Rust-backed Python classes cannot be used as baseclasses (for
rust-cpython anyway), we use composition rather than inheritance.
This also allows us to keep the IO operations in the Python side, removing
(for now) the need to rewrite VFS in Rust, which would be a heavy undertaking.
Differential Revision: https://phab.mercurial-scm.org/D6634
#testcases bdiff xdiff
#if xdiff
#require xdiff
$ cat >> $HGRCPATH <<EOF
> [experimental]
> xdiff = true
> EOF
#endif
Test case that makes use of the weakness of patience diff algorithm
$ hg init
>>> open('a', 'wb').write(('\n'.join(list('a' + 'x' * 10 + 'u' + 'x' * 30 + 'a\n'))).encode('ascii')) and None
$ hg commit -m 1 -A a
>>> open('a', 'wb').write(('\n'.join(list('b' + 'x' * 30 + 'u' + 'x' * 10 + 'b\n'))).encode('ascii')) and None
#if xdiff
$ hg diff
diff -r f0aeecb49805 a
--- a/a Thu Jan 01 00:00:00 1970 +0000
+++ b/a Thu Jan 01 00:00:00 1970 +0000
@@ -1,4 +1,4 @@
-a
+b
x
x
x
@@ -9,7 +9,6 @@
x
x
x
-u
x
x
x
@@ -30,6 +29,7 @@
x
x
x
+u
x
x
x
@@ -40,5 +40,5 @@
x
x
x
-a
+b
#else
$ hg diff
diff -r f0aeecb49805 a
--- a/a Thu Jan 01 00:00:00 1970 +0000
+++ b/a Thu Jan 01 00:00:00 1970 +0000
@@ -1,15 +1,4 @@
-a
-x
-x
-x
-x
-x
-x
-x
-x
-x
-x
-u
+b
x
x
x
@@ -40,5 +29,16 @@
x
x
x
-a
+u
+x
+x
+x
+x
+x
+x
+x
+x
+x
+x
+b
#endif