Merge branch 'ab/tests-various-fixup'
Various test updates.
* ab/tests-various-fixup:
rm tests: actually test for SIGPIPE in SIGPIPE test
archive tests: use a cheaper "zipinfo -h" invocation to get header
upload-pack tests: avoid a non-zero "grep" exit status
git-svn tests: rewrite brittle tests to use "--[no-]merges".
git svn mergeinfo tests: refactor "test -z" to use test_must_be_empty
git svn mergeinfo tests: modernize redirection & quoting style
cache-tree tests: explicitly test HEAD and index differences
cache-tree tests: use a sub-shell with less indirection
cache-tree tests: remove unused $2 parameter
cache-tree tests: refactor for modern test style