Re: [PATCH v2] doc: checkout: rewrite detached HEAD state explanation

[Junio C Hamano <gitster@pobox.com>]

"Julia Evans via GitGitGadget" <gitgitgadget@gmail.com> writes:

> Write a new explanation addressing these issues, and put it in a
> standalone guide so that we can easily reference it from advice
> ("see `git help detachedhead`").

Isn't it 'git help detached-head' in this edition?

> Co-authored-by: Marie Claire LeBlanc Flanagan <hello@marieflanagan.com>
> Signed-off-by: Julia Evans <julia@jvns.ca>

Can the other author also sign it off?

> +Git will eventually permanently delete those "garbage" commits during
> +garbage collection. Those commits will be deleted after 90 days by
> +default, see linkgit:git-gc[1] for more.

Does this say 90 days because that is the gc.reflogExpire retention?

If you create a commit, change your mind, rewind the tip of the
branch (e.g., with "git commit --amend"), and then keep working, the
original commit before amending would be unreachable from the tip of
that branch.  Its reflog entry would then expire after
gc.reflogExpireUnreachable, which defaults to 30 days.  If your
commit were created on a detached HEAD, I am not sure offhand how
the thresholds for gc.reflogExpire and gc.reflogExpireUnreachable
come into play for HEAD, as HEAD by default flips back and forth
regularly across branch tips that are not reachable from each other.
When "gc" kicks in, the commit HEAD currently points to is unlikely
to reach the abandoned commit.

It might be safer to either say "after 30 days by default" or
generalize it to "after a few weeks by default" to avoid being
overly prescriptive.

> diff --git a/advice.c b/advice.c
> index 401d047391..43f86c2eaf 100644
> --- a/advice.c
> +++ b/advice.c
> @@ -291,6 +291,7 @@ void detach_advice(const char *new_name)
>  	"\n"
>  	"  git switch -\n"
>  	"\n"
> +	"Run `git help detachedhead` to learn more.\n"

"git help deatched-head" here, too.

>  	fprintf(stderr, fmt, new_name);
> diff --git a/command-list.txt b/command-list.txt
> index 63ae2a67c9..922a1dbd84 100644
> --- a/command-list.txt
> +++ b/command-list.txt
> @@ -218,6 +218,7 @@ gitcore-tutorial                        guide
>  gitcredentials                          guide
>  gitcvs-migration                        guide
>  gitdatamodel                            guide
> +gitdetached-head                         guide
>  gitdiffcore                             guide
>  giteveryday                             guide
>  gitfaq                                  guide

This seems to be manually aligned with SP, so compensate the
addition of "-" between detached and head by removing one SP before
guide on the same line.

Thanks.