Re: [PATCH] Revert 'diff-merges: let "-m" imply "-p"'

Junio C Hamano [off-list ref] writes:

quoted

Similarly, a script author could include

	git log -m --first-parent --format=%H -- README

to filter the first-parent history for commits that modified README.
The -m is a no-op but it reflects the script author's intent.

So the expectation is with "-m" we'd give single parent commits on
the fp chain, and merges from side branches that change README, in
addition to merges from side branches that was forked way before the
README was updated on the trunk (hence had ancient README but the
merge kept the version from the trunk)?

quoted

For
example, until 1e20a407fe2 (stash list: stop passing "-m" to "git
log", 2021-05-21), "git stash list" did this.

This is not a example that supports your conclusion, though.  The
reason why 288c67ca (stash: default listing to working-tree diff,
2014-08-06) added "-m" on the command line to make it:

  git log --format="%gd: %gs" -g --first-parent -m "$@" $ref_stash --

is to prepare for the users who may pass "-p" as part of the "$@";
they wil get no patches out of these merge commits that represent
stash entries otherwise, and they'd have to pass "-m -p" instead,
without the change.

quoted

As a result, we can't safely change "-m" to imply "-p" without fear of
breaking such scripts.  Restore the previous behavior.

So the above is *not* an example of a script that would have been
broken with this change.

Sorry, I have to take 70% of the above back.  While it is *not* an
example that shows an author's intent that changes from not just
trunk but all side branches to README are to be shown, the original
left after 288c67ca (stash: default listing to working-tree diff,
2014-08-06) would have been broken by the change you are proposing
to revert.  It used to be just "if you give -p we'll show a patch"
but if we make "-m" to mean "-m -p", it does get broken.

Which is BAD.

I am inclined to take the revert, but I do not think reverting it
alone will break more things than it fixes.

For example, 1e20a407 (stash list: stop passing "-m" to "git log",
2021-05-21) that dropped "-m" must be reverted as well, no?

Junio C Hamano wrote:

For example, 1e20a407 (stash list: stop passing "-m" to "git log",
2021-05-21) that dropped "-m" must be reverted as well, no?

No, that change is fine.  The "-m" doesn't have an effect one way or
another after this revert.

Thanks,
Jonathan