Re: [PATCH] Cygwin: Improve FAQ on early breakpoint for ASLR

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi Jon,

On Wed, 14 Dec 2022, Jon Turney wrote:

> On 11/12/2022 14:45, Johannes Schindelin wrote:
> > On December 11, 2022 2:54:02 PM GMT+01:00, Jon Turney
> > <jon.turney@dronecode.org.uk> wrote:
> > > On 05/12/2022 15:23, Johannes Schindelin wrote:
> > > > On Mon, 28 Nov 2022, Corinna Vinschen wrote:
> > > > > On Nov 28 13:00, Jon Turney wrote:
> > > > > > On 15/11/2022 10:46, Corinna Vinschen wrote:
> > > > > > >
> > > > > > > It would be great if we could get used to using the same syntax as
> > > > > > > the
> > > > > > > Linux kernel project to document stuff.  I'm trying to follow
> > > > > > > their lead
> > > > > > > for a while.  For fixes to former commits, it looks like this in
> > > > > > > the
> > > > > > > kernel, at the end of the commit message:
> > > > > > >
> > > > > > > Fixes: 123456789012 ("title of commit 123456789012")
> > > > > > >
> > > > > > > Yeah, core.abbrev is 12 digits.  I'm using this setting for quite
> > > > > > > some
> > > > > > > time locally.
> > > > > >
> > > > > > Sounds good.  Is there some script to automate generating this kind
> > > > > > of
> > > > > > comment from a commit-id?
> > > > >
> > > > > I don't think so, at least I don't see anything like that in git
> > > > > docs...
> > > >
> > > > It's note _quite_ what you asked for, but `git show --pretty=reference
> > > > -s
> > > > <commit>` (https://git-scm.com/docs/git-show#_pretty_formats) gives you
> > > > _almost_ what you are looking for.
> > > >
> > > > But you can always call `git show -s --format='%h ("%s")' <commit>`, and
> > > > even configure an alias for this:
> > > >
> > > >  git config --global alias.pretty-print-commit \
> > > >   "-c core.abbrev=12 show -s --format='%h (\"%s\")'"
> > > >
> > > Thanks!
> > >
> > > I added '-c core.pager=', but this is what I was looking for, to save a
> > > bit of copying and pasting and editing.
> > >
> >
> > Better use `git -P`, then... (see
> > https://git-scm.com/docs/git#Documentation/git.txt--P for full details)
> >
>
> I started off with that, but that fails when used with:
>
> fatal: alias 'pretty-print-commit' changes environment variables.
> You can use '!git' in the alias to do this
>
> ... which I'm sure tells me the right way to write this :)

My apologies for leading you on this windy path through Git's obscure and
intricate internals.

The problem is that the `-P` option claims to change the environment (see
https://github.com/git/git/blob/v2.40.0/git.c#L176-L179), and aliases are
not allowed to do that.

You _can_ work around that by using `!git -P [...]`, i.e. by forcing a
shell to be spawned that then spawns `git`. But that is wasteful,
especially given the performance characteristics of spawning processes in
Cygwin.

Therefore, your `-c core.pager=` solution is much preferable to my
suggestion to use `-P`.

Ciao,
Johannes