Revision Log should not allow viewing changes out-of-order

[jrivers@…]

When viewing the revision log for a file, the default option is set up so that pressing "View Changes" will give you a diff for the last revision of the file, which is fine. However, the user can easily make trac give you a backwards diff, for which the output is confusing (a change where text was deleted says that text was added instead).

I suggest something like Wikipedia's interface, where it's impossible to see this kind of diff. Another option would be to provide a warning to the user if they tried that, or to detect it and show a forward diff.

If there is a real reason to show a backwards diff, perhaps a special option could be enabled somewhere...

(sorry for not knowing the component)

[cboos]

Yes, this is worth considering for the following reasons:

• the column containing the radio buttons doesn't say anything about which is the old, which is the new rev
• in order to be consistent with the Wiki Page History, which always shows forward diffs
• getting a backward diff is occasionally useful (e.g. for generating a diff to revert changes), but it's easy to get there from the "forward" diff view, by following the Reverse Diff found there

So a bit a Javascript magic is in order ;)

[osimons]

I hadn't even noticed the 'Reverse diff' option before now :-)

Anyway, I don't think comparing wiki features with version control on this is all that useful - having the option by radio buttons to diff both ways is somewhat useful.

Here is a very simple solution: We put an arrow in the column header that points to the right. That should to any (most) that deal with source code imply the 'from' and 'to'. If the radios are reversed it should be (somewhat) equally obvious that you get a reverse diff.

Lastly, we could also consider jquery magic to switch the direction of the arrows if from > to, with just an em-dash if the selection is the same (ie. no no diff). The left-to-right arrow would however work fine with javascript disabled as well, so no dependency on it for the general clarification.

[cboos]

I agree that getting a reverse diff directly from the log is useful, we should keep this feature.

In r8412, I added some hints about the role of the radiobuttons, this is hopefully enough to address the usability concerns raised here.