Re: [PATCH] Teach git log --check to return an appropriate error code

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

Hmm, good point.

The bit will never be cleared during a single diff run by design, because it needs to be cumulative in order to check a patch that describes changes to multiple paths --- iow, the API sequence is (1) the caller to the diff machinery resets the bit to zero and then (2) the caller exercises the diff machinery and expects the machinery to set the bit if even a single failure is detected, or leaves it unset if there is none.

So unless you (log_tree_diff(), the caller of diff machinery), decide to explicitly reset the bit (or decide to use a freshly allocated and initialized diff_options for each commit it feeds diff_tree_sha1()), the assumption would hold. We need to see how plausible it would be for us to break that assumption in the future.

Future versions of log_tree_diff() may want to tweak opt->diffopt per commit, when we have options for "use larger -U<lines> value after hitting this commit", or "use this pathspec to limit the diff output after hitting this commit", for example. But even in these cases, I think it is implausible to start from a freshly initialized diff_options structure. The code most likely would start from the copy of what was in use and update only the necessary fields, without disturbing the state variables.

So I think you are worried a bit too much in this case, even though it is a valid concern in principle. It might warrant a comment somewhere inside log_tree_diff() to tell people not to re-initialize opt->diffopt per commit without thinking, though.

One interesting option that might be interesting to add to the log family would be to show only commits that fail the checkdiff tests. I suspect necessary change for doing so would go to log_tree_diff() codepath.