why are covered lines changing from build to build?

[daira]

E.g. see the changed files in ​https://coveralls.io/builds/1188907, which is a doc-only commit.

[daira]

(2014-09-23 18:49:52) zooko: Does anybody know why coveralls say that coverage decreased here? https://github.com/tahoe-lafs/tahoe-lafs/pull/110#issuecomment-56559949
(2014-09-23 18:50:02) zooko: Better yet, can I find a diff of coverage before and after that PR?
(2014-09-23 18:50:36) warner: the coveralls site shows which files are up/down (or both at the same time, weirdly)
(2014-09-23 18:50:52) warner: it's not as readable as it could be
(2014-09-23 18:51:16) ***zooko looks at https://coveralls.io/builds/1246883
(2014-09-23 18:51:38) zooko: So this page https://coveralls.io/builds/1246883 is all about this one PR.
(2014-09-23 18:53:26) warner: looks like 5 lines in mutable/publish.py ..
(2014-09-23 18:53:50) ***zooko looks at https://coveralls.io/files/297721106
(2014-09-23 18:54:03) warner: urgh, it shows which lines are covered/uncovered, and how many changed, but it doesn't say *which* lines changed
(2014-09-23 18:54:16) zooko: Oh cool there's a button to "previous job": https://coveralls.io/files/290358568
(2014-09-23 18:54:23) zooko: Now I flip back and forth until I see it... :-)
(2014-09-23 18:55:10) zooko: line 451
(2014-09-23 18:55:23) zooko: That's 3 of the lines ...
(2014-09-23 18:55:29) warner: one job had some bad shares, the other didn't
(2014-09-23 18:55:31) zooko: This process of spotting the difference needs automation. :-(
(2014-09-23 18:55:35) warner: yeah
(2014-09-23 18:55:49) warner: two more lines at 496
(2014-09-23 18:55:59) warner: which is the same thing, lack of bad shares
(2014-09-23 18:56:17) warner: what did the PR change?

[exarkun]

The tools are a problem, yes. coveralls.io has garbage collected a lot of the details of the builds linked in the above conversation, though. This ticket is not actionable.