Subject: Re: Extending and updating gitglossary

From: [email-masked] (Jakub Narębski)
Date: Tue, 10 Nov 2020 02:35:46 +0100

Hello Philip,

Philip Oakley <[email-masked]> writes:
> On 06/11/2020 18:26, Jakub Narębski wrote:
>> Junio C Hamano <[email-masked]> writes:
>>> Philip Oakley <[email-masked]> writes:
>>>
>>>> This may be not part of the the main project, but could you consider, if
>>>> time permits, also adding some entries into the Git Glossary (`git help
>>>> glossary`) for the various terms we are using here and elsewhere, e.g.
>>>> 'topological levels', 'generation number', 'corrected commit date' (and
>>>> its fancy technical name for the use of date heuristics e.g. the
>>>> 'chronological ordering';).
>>>>
>>>> The glossary can provide a reference, once the issues are resolved. The
>>>> History Simplification and Commit Ordering section of git-log maybe a
>>>> useful guide to some of the terms that would link to the glossary.
>>>
>>> Ah, I first thought that Documentation/rev-list-options.txt (which
>>> is the relevant part of "git log" documentation you mention here)
>>> already have references to deep technical terms explained in the
>>> glossary and you are suggesting Abhishek to mimic the arrangement by
>>> adding new and agreed-upon terms to the glossary and referring to
>>> them from the commit-graph documentation updated by this series.
>>>
>>> But sadly that is not the case.  What you are saying is that you
>>> noticed that rev-list-options.txt needs a similar "the terms we use
>>> to explain these two sections should be defined and explained in the
>>> glossary (if they are not) and new references to glossary should be
>>> added there" update.

What terms you feel need glossary entry?

>>> In any case, that is a very good suggestion.  I agree that updating
>>> "git log" doc may be outside the scope of Abhishek's theme, but it
>>> would be very good to have such an update by anybody ;-)
>>
>> The only possible problem I see with this suggestion is that some of
>> those terms (like 'topological levels' and 'corrected commit date') are
>> technical terms that should be not of concern for Git user, only for
>> developers working on Git.  (However one could encounter the term
>> "generation number" in `git commit-graph verify` output.)

To be more precise, I think that user-facing glossary should include
only terms that appear in user-facing documentation and in output
messages of Git commands (with the possible exception of maybe output
messages of some low-level plumbing).

I think that the developer-facing glossary should include terms that
appear in technical documentation, and in commit messages in Git
history.

> However we do mention "topolog*"  in a number of the manual pages, and
> rather less, as yet, in the technical pages.
>
> "Lexicographic" and "chronological" are in the same group of fancy
> technical words ;-)

I think that 'topological level' would appear only in technical
documentation; if it would be the case then there is no reason to add it
to user-facing glossary (to gitglossary manpage).

'Topological order' or 'topological sort', 'lexicographical order' and
'chronological order' are not Git-specific terms, and there are no
Git-specific ambiguities.  I am therefore a bit unsure about adding them
to *Git* glossary.

- In computer science, a _topological sort_ or _topological_ ordering of
  a directed graph is a linear ordering of its vertices such that for
  every directed edge uv from vertex u to vertex v, u comes before v in
  the ordering.

  For Git it means that top to bottom, commits always appear before
  their parents. With `--graph` or `--topo-order` Git also avoids
  showing commits on multiple lines of history intermixed.

- In mathematics, the _lexicographic_ or _lexicographical order_ (also
  known as lexical order, dictionary order, etc.) is a generalization of
  the alphabetical order.

  For Git it is simply alphabetical order.

- _Chronological order_ is the arrangement of things following one after
  another in time; or in other words date order.

  Note that `git log --date-order` commits also always appear before
  their parents, but otherwise commits are shown in the commit timestamp
  order (committer date order)

>>
>> I don't think adding technical terms that the user won't encounter in
>> the documentation or among messages that Git outputs would be not a good
>> idea.  It could confuse users, rather than help them.
>>
>> Conversely, perhaps we should add Documentation/technical/glossary.txt
>> to help developers.
>
> I would agree that the Glossary probably ought to be split into the
> primary, secondary and background terms so that the core concepts are
> separated from the academic/developer style terms.

I don't thing we need three separate layers; in my opinion separating
terms that user of Git might encounter from terms that somebody working
on developing Git may encounter would be enough.

The technical glossary / dictionary could also help onboarding...

>
> Git does rip up most of what folks think about version "control",
> usually based on the imperfect replication of physical artefacts.

I don't quite understand what you wanted to say there.  Could you
explain in more detail, please?

>> P.S. By the way, when looking at Documentation/glossary-content.txt, I
>> have noticed few obsolescent entries, like "Git archive", few that have
>> description that soon could be or is obsolete and would need updating,
>> like "master" (when default branch switch to "main"), or "object
>> identifier" and "SHA-1" (when Git switches away from SHA-1 as hash
>> function).
>
> The obsolescent items can be updated. I'm expecting that the 'main' and
> 'SHA-' changes will eventually be picked up as part of the respective
> patch series, hopefully as part of the global replacements.

Here I meant that "Git archive" entry is not important anymore, as I
think there are no active users of GNU arch version control system (no
"arch people"); arch's last release was in 2006, and its replacement,
Bazaar (or 'bzr') doesn't use this term. So I think it can be safely
removed in 2020, after 14 years after last release of arch.

In most cases "SHA-1" in the descriptions of terms in glossary should be
replaced by "object identifier" (to be more generic).  This can be
safely done before switch to NewHash is ready and announced.

Best,
-- 
Jakub Narębski