Re: [PATCH] rev-parse: Fix shell scripts whose cwd is a symlink into a git work-dir

>> AFAIR, it was introduced to make test-builds of really large projects in
>> really deep directories with a ton of symlinks leading to the path work a
>> lot faster.
> 
> Andreas,
> 
> I see value in keeping Git very fast.  That is, after all, why I chose
> Git over Mercurial.  Do you know where that discussion was, if was in
> the archives?  I found these reasons to avoid absolute paths in the git
> archives:
> 
> * paths with more components are slower to work with (in the context of
>   add and diff, which deal with many many paths)
> * absolute paths may exceed PATH_MAX while relative ones didn't
> * getcwd() will fail if parent directories are not executable, or on
>   some platforms, if parent directories are not readable
> 
> My impression is that the performance issue is probably not significant
> for cd_to_toplevel since it's not in a tight inner loop, and dito for
> other potential callers of --show-cdup.  The PATH_MAX seems to be a
> restriction elsewhere in the code already.
> 

> Even if there were a scenario that put --show-cdup in a tight loop, I
> wonder whether current implementation provides much performance benefit,
> at least when bash is the calling language: bash seems to make the
> relative path absolute anyway inside the "cd" builtin.
> 
> The commit (5f94c730) that introduces that code doesn't mention
> performance.  It compares to:
> 
>   git rev-parse --show-prefix | sed -e 's|[^/][^/]*|..|g'
> 
> 
> I also noticed that this failure case with "--show-cdup" in a symlinked
> directory has come up more than once before.
> http://marc.info/?l=git&m=122452534912000&w=2
> http://marc.info/?l=git&m=121613416212958&w=2
> https://kerneltrap.org/mailarchive/git/2007/4/25/244653/thread
>