narrow: check for servers' narrow support before doing anything (BC)
Recently we introduced narrow capabilities for the server. So we can check
whether a server has narrow clone support or not before doing anything. This is
BC because new clients won't be able to extend from old narrow-enabled servers.
I *think* narrow is not used much (maybe just inside Google), also it's
experimental so I think we can change this. We will need to this someday anyway.
The "doesn't" in error is changed to "does not" because I think that's we do in
core. I also changed one more instance of the error message to use 'does not'
for consistency.
Differential Revision: https://phab.mercurial-scm.org/D4789
#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