largefiles: use util.sha1() instead of hashlib.sha1() everywhere

tests: check for svn >= 1.3 and >= 1.5 in tests that require those versions

convert: add missing import of util, needed for svn < 1.6

run-tests: make sure no_proxy/NO_PROXY are empty to fix test-http-proxy.t If no_proxy (or NO_PROXY) includes localhost, the test for detecting an unreachable proxy fails, because the proxy setting is ignored.

largefiles: test "lfconvert --to-normal" with rename/remove/merge This gets us very close to full test coverage of lfconvert. The only features not tested are: - .hgtags conversion - abort when largefile becomes symlink

largefiles: test lfconvert with rename, remove, and merge

largefiles: beef up test-lfconvert.t so it's more thorough - instead of converting a single changeset with a single file, convert two changesets which each add a mix of normal and large files - make one of the large files not-so-large, but identified as large by filename - use shorter, simpler filenames - put some files in a subdirectory - test that file contents are correctly converted - drop unnecessary cleanup step

largefiles: rearrange how lfconvert detects non-local repos Mainly this is so we can test that code; it has the side benefit of not requiring network I/O to reject non-local repo URLs.

largefiles: test lfconvert error handling; remove redundant code

largefiles: extract test-lfconvert.t from test-largefiles.t test-largefiles.t is getting pretty big, and there's lots more to test in lfconvert. And lfconvert is a fairly orthogonal feature to the rest of largefiles.