git-log diff formatting options: some turn on diffs, some don't

If you run git log -c this implies the -p flag.  But git log -r does not imply -p, even though both -r and -c are flags which exist to 'control the formatting of diff output' according to the documentation.

I think that all the flags listed in that section should implicitly turn on -p if it wasn't given.  (I'd also be content if they died with an error when -p wasn't given, but that could break existing users.)  The current behaviour is inconsistent and a bit of a headscratcher when 'git log -r' produces the same output as plain 'git log'.

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Ed Avis <eda@waniasset.com> writes:

`-r` does not control the formatting, actually. It has no effect in the Porcelain "git diff" and "git log"---it is always on and there may not even be a way to turn it off (so, effectively it is a no-op).

The only case I offhand recall that `-r` makes difference is when running `git diff-tree`, whose default output format is the `--raw` format. `git diff-tree A B` and `git diff-tree -r A B` both give its output in the raw format, but if there are differences in the contents of the subdirectory between A and B, the former just shows the subdirectory without showing which paths in that subdirectory differ, while the latter shows the individual paths. For obvious reasons, the '-r' option must *not* imply '-p' for this command, to which the `-r` option has any effect.

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Thanks for your reply. If the -r flag has no effect on 'git log' then shouldn't it be omitted from the documentation? https://git-scm.com/docs/git-log has a section on 'Diff Formatting' but if I understand you rightly, a large part of that only applies to other commands.

Further, I would suggest that if the -r flag does get passed to 'git log' then it should give a warning. (Ideally I would say an error, but there might be existing scripts that pass it.)

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