run-tests.py: fix diff output when test-foo.out doesn't exist.
Previously, if test-foo.out doesn't exist and test-foo outputs
something, the first line of the diff will look like this:
-+changeset: 0:0acdaf898367
(note the leading "-")
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Main should be gone
a
changeset: 3:ded32b0db104
tag: tip
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added side2
changeset: 2:92a816cea698
parent: 0:537353581d3d
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added side1
changeset: 1:221226fb2bd8
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added main
changeset: 0:537353581d3d
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added a
Should have two heads, side2 and main
changeset: 3:ded32b0db104
tag: tip
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added side2
changeset: 1:221226fb2bd8
user: test
date: Mon Jan 12 13:46:40 1970 +0000
summary: Added main
Should show a side1 side2
a
side1
side2
resolving manifests
force 1 allow None moddirstate True linear False
ancestor 8515d4bfda76 local 1c0f48f8ece6 remote 0594b9004bae
remote deleted side2, clobbering
remote deleted side1, clobbering
remote created main
getting main
removing side1
removing side2
1 files updated, 0 files merged, 2 files removed, 0 files unresolved
Should only show a main
a
main