Re: [PATCH] documentation: add tutorial for revision walking

[Emily Shaffer <emilyshaffer@google.com>]

On Mon, Jun 10, 2019 at 01:49:41PM -0700, Junio C Hamano wrote:
> Emily Shaffer <emilyshaffer@google.com> writes:
> 
> > +My First Revision Walk
> > +======================
> > +
> > +== What's a Revision Walk?
> > +
> > +The revision walk is a key concept in Git - this is the process that underpins
> > +operations like `git log`, `git blame`, and `git reflog`. Beginning at HEAD, the
> > +list of objects is found by walking parent relationships between objects. The
> > +revision walk can also be usedto determine whether or not a given object is
> > +reachable from the current HEAD pointer.
> 
> s/usedto/used to/;
Done.
> 
> > +We'll put our fiddling into a new command. For fun, let's name it `git walken`.
> > +Open up a new file `builtin/walken.c` and set up the command handler:
> > +
> > +----
> > +/*
> > + * "git walken"
> > + *
> > + * Part of the "My First Revision Walk" tutorial.
> > + */
> > +
> > +#include <stdio.h>
> 
> Bad idea.  In the generic part of the codebase, system headers are
> supposed to be supplied by including git-compat-util.h (or cache.h
> or builtin.h, that are common header files that begin by including
> it and are allowed by CodingGuidelines to be used as such).
Done.
> 
> > +#include "builtin.h"
> > +
> > +int cmd_walken(int argc, const char **argv, const char *prefix)
> > +{
> > +        printf(_("cmd_walken incoming...\n"));
> > +        return 0;
> > +}
> > +----
> 
> I wonder if it makes sense to use trace instead of printf, as our
> reader has already seen the psuh example for doing the above.

Hmmm. I will think about it and look into the intended use of each. I
hadn't considered using a different logging method.

> 
> > +Add usage text and `-h` handling, in order to pass the test suite:
> 
> It is not wrong per-se, and it indeed is a very good practice to
> make sure that our subcommands consistently gives usage text and
> short usage.  Encouraging them early is a good idea.
> 
> But "in order to pass the test suite" invites "eh, the test suite
> does not pass without usage and -h?  why?".
> 
> Either drop the mention of "the test suite", or perhaps say
> something like
> 
> 	Add usage text and `-h` handling, like all the subcommands
> 	should consistently do (our test suite will notice and
> 	complain if you fail to do so).
> 
> i.e. the real purpose is consistency and usability; test suite is
> merely an enforcement mechanism.

Yeah, you're right. I'll reword this.

> 
> > +----
> > +{ "walken", cmd_walken, RUN_SETUP },
> > +----
> > +
> > +Add it to the `Makefile` near the line for `builtin\worktree.o`:
> 
> Backslash intended?

Nope, typo.


Thanks for the comments, Junio.

 - Emily