Re: [PATCH v3 6/6] Use the early config machinery to expand aliases

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 13, 2017, 16:21 UTC
Message-ID: <xmqqk24f97ud.fsf@gitster.mtv.corp.google.com>
In-Reply-To: <822765b002488f03523bf440097492be3c14931a.1497355444.git.johannes.schindelin@gmx.de>

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

> Instead of discovering the .git/ directory, read the config and then
> trying to painstakingly reset all the global state if we did not find a
> matching alias, let's use the early config machinery instead.

s/read/&ing/, I think. My reading hiccupped while trying to figure out what two alternative approaches are being compared.

Show 7 quoted lines

> It may look like unnecessary work to discover the .git/ directory in the
> early config machinery and then call setup_git_directory_gently() in the
> case of a shell alias, repeating the very same discovery *again*.
> However, we have to do this as the early config machinery takes pains
> *not* to touch any global state, while shell aliases expect a possibly
> changed working directory and at least the GIT_PREFIX and GIT_DIR
> variables to be set.

Makes sense.  Nicely explained.

> Also, one might be tempted to streamline the code in alias_lookup() to
> *not* use a strbuf for the key. However, if the config reports an error,
> it is far superior to tell the user that the `alias.xyz` key had a
> problem than to claim that it was the `xyz` key.

The mention of "streamline" is puzzling to me. When we are trying "git xyz", "alias.xyz" is the key we would look up, not "xyz"; it is not clear to anybody who didn't read the discussion on v2 (which includes the readers of "git log" in a few months) what kind of flawed streamlining could look up "xyz" and result in a bad configuration reported on it.

>  alias.c          | 31 ++++++++++++++++++++++++-------
>  git.c            | 55 ++++---------------------------------------------------
>  t/t7006-pager.sh |  2 +-
>  3 files changed, 29 insertions(+), 59 deletions(-)

Happy to see the deletion of all the save/restore-env stuff.

Except for the puzzlement in one paragraph in the log, looks very good. Thanks for a pleasant reading.