Re: [lmi] [lmi-commits] master 783f4dd 5/9: Consolidate and revise documentation

[Greg Chicares]

On 2018-04-28 16:39, Vadim Zeitlin wrote:
> On Sat, 28 Apr 2018 01:22:34 +0000 Greg Chicares <address@hidden> wrote:
[...]
> GC> Okay, I've tried to do that for class wx_table_generator::column_info
> GC> in commit c9f958f6cb904.
> 
>  Sorry, I don't see any such commit. Is it not pushed yet or did you mean a
> different commit perhaps?

This looks really frightening, 'xanadu' being my alias for github,
where I have no account and cannot have committed anything:

  /opt/lmi/src/lmi[0]$git describe --all c9f958f6cb904
  remotes/xanadu/master-22-gc9f958f6

Yet paging back in the terminal confirms that I did commit that SHA1:

  /opt/lmi/src/lmi[0]$git commit --all
  ...
  [master c9f958f6] Move most commentary out of a class declaration
   1 file changed, 23 insertions(+), 31 deletions(-)

and confirms that I haven't switched branches at all recently:

  /opt/lmi/src/lmi[0]$git branch
  * master
    odd/vector-fwd-decl

However, this is the commit I really mean:

  /opt/lmi/src/lmi[0]$git describe --all 2dd92c91                          
  heads/master

I had committed c9f958f6cb904 and copied that SHA1 into my email.
Then, reviewing the commit one last time before pushing, I saw a
one-character typing mistake, and fixed it:

  /opt/lmi/src/lmi[0]$git commit --amend
  ...
  [master 2dd92c91] Move most commentary out of a class declaration

...and pushed it without updating the email:

  /opt/lmi/src/lmi[0]$git push
  ...
  To git.sv.gnu.org:/srv/git/lmi.git
     9fd812bc..2dd92c91  master -> master

...so it was my msitake not to update the email. As for this mystery:

  /opt/lmi/src/lmi[0]$git describe --all c9f958f6cb904
  remotes/xanadu/master-22-gc9f958f6

I don't know why git-describe says that. It seems unlikely that we've
found a collision on a 13-character SHA1 between savannah and github,
especially because using the full SHA1 doesn't make a difference:

  /opt/lmi/src/lmi[0]$git rev-parse --default master --verify c9f958f6cb904
  c9f958f6cb904f25efbcd7272f819de36bb78c65
  /opt/lmi/src/lmi[0]$git describe --all 
c9f958f6cb904f25efbcd7272f819de36bb78c65
  remotes/xanadu/master-22-gc9f958f6

and if I inspect both SHA1s thus:

  /opt/lmi/src/lmi[0]$git show 2dd92c91
  /opt/lmi/src/lmi[0]$git show c9f958f6cb904

they differ only in the single character that I git-commit-amended.
I can only guess that '--amend' causes the old SHA1 to become invalid
for purposes of 'git describe', which then returns a meaningless string.