Re: [PATCH/WIP v3 07/31] am: extract patch, message and authorship with git-mailinfo

From: Junio C Hamano <gitster@pobox.com>
Date: Jun 24, 2015, 15:59 UTC
Message-ID: <xmqqa8vpayhg.fsf@gitster.dls.corp.google.com>
In-Reply-To: <20150624075446.GA1964@yoshi.chippynet.com>

Paul Tan <pyokagan@gmail.com> writes:

> 3. I'm over-thinking this and you just want the "struct strbufs" in the
>    struct am_state to be switched to "char*"s?

Yes, everybody interacts with am_state, and these fields are supposed to be constant during the processing of each patch input message; they should be simple strings, not strbufs, to make sure if anybody _does_ muck with them in-place, that would be very visible. The helpers to initialize them are free to use strbuf API to prepare these simple string fields, of course.

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> (On a somewhat related thought, currently we do write_file() all over
> the place, which is really ugly. I'm leaning heavily on introducing an
> am_save() function, for "I don't care how it is done but just update the
> contents of the am state directory so that it matches the contents of
> the struct am_state".

Sure; the scripted Porcelain may have done "echo here, echo there" instead of "concatenate into a $var and then 'echo $var' at end" as that is more natural way to program in that environment. You are doing this in C and "prepare the thing in-core and write it all at the point to snapshot" may well be the more natural way to program.

As long as a process that stops in the middle does not leave on-disk state inconsistent, batching would be fine. For example, you may apply and commit two (or more) patches without updating the on-disk state as you do not see need to give control back to the user (i.e. they applied cleanly) and then write out the on-disk state with .next incremented by two (or more) before giving the control back could be a valid optimization (take this example with a grain of salt, though; I haven't thought too deeply about what should happen if you Ctrl-C the process in the middle).