pull: allow a generic way to pass parameters to the pull operation
We have been feeling the need for this in extensions for quite some time. This
will be used to pass remote bookmark information around in the next changesets.
$ hg init
$ touch a
$ hg add a
$ hg ci -m "a"
$ echo 123 > b
$ hg add b
$ hg diff --nodates
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
$ hg diff --nodates -r tip
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
$ echo foo > a
$ hg diff --nodates
diff -r 3903775176ed a
--- a/a
+++ b/a
@@ -0,0 +1,1 @@
+foo
diff -r 3903775176ed b
--- /dev/null
+++ b/b
@@ -0,0 +1,1 @@
+123
$ hg diff -r ""
hg: parse error: empty query
[255]
$ hg diff -r tip -r ""
hg: parse error: empty query
[255]