Re: gitignore vs. exclude vs assume-unchanged?

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

alex@bellandwhistle.net writes:

> Any clarification on the differences much appreciated:
>
> http://stackoverflow.com/questions/23097368/git-ignore-vs-exclude-vs-assume-unchanged/23097509

Please don't force people to refer to external site.

The .gitignore and .git/info/exclude are the two UIs to invoke the
same mechanism.  In-tree .gitignore are to be shared among project
members (i.e. everybody working on the project should consider the
paths that match the ignore pattern in there as cruft).  On the
other hand, .git/info/exclude is meant for personal ignore patterns
(i.e. you, while working on the project, consider them as cruft).

Assume-unchanged should not be abused for an ignore mechanism.  It
is "I know my filesystem operations are slow.  I'll promise Git that
I won't change these paths by making them with that bit---that way,
Git does not have to check if I changed things in there every time I
ask for 'git status' output".  It does not mean anything other than
that.  Especially, it is *not* a promise by Git that Git will always
consider these paths are unmodified---if Git can determine a path
that is marked as assume-unchanged has changed without incurring
extra lstat(2) cost, it reserves the right to report that the path
*has been* modified (as a result, "git commit -a" is free to commit
that change).