convert: workaround for cvsps.cache under Windows
In non-cygwin environment, cvsps fails to create its cache directory and redirect its output to stderr. Just ignore the error and capture stderr as well.
EVERYTHING
diff -r ec612a6291f1 alpha/one
--- a/alpha/one
+++ b/alpha/one
@@ -0,0 +1,1 @@
+1
diff -r ec612a6291f1 beta/two
--- a/beta/two
+++ b/beta/two
@@ -0,0 +1,1 @@
+2
BETA ONLY
diff -r ec612a6291f1 beta/two
--- a/beta/two
+++ b/beta/two
@@ -0,0 +1,1 @@
+2
INSIDE BETA
diff -r ec612a6291f1 beta/two
--- a/beta/two
+++ b/beta/two
@@ -0,0 +1,1 @@
+2