Re: [RFC] [pre-commit] Add check-new-file-license

[Tom de Vries <tdevries@suse.de>]

On 6/17/26 7:45 PM, Tom Tromey wrote:
>>>>>> "Tom" == Tom de Vries <tdevries@suse.de> writes:
> 
> Tom> I forgot to add a copyright notice to a file.
> Tom> I came across gdb/contrib/license-check-new-files.sh, and ran it out of
> Tom> curiosity, and it pointed out the file.
> 
> I didn't know about this file.  Weird that it has a '.sh' extension.
> 

Yeah.  Renaming it to .py show some pre-commit errors:
...
gdb/contrib/license-check-new-files.py:58:5: E722 do not use bare 'except'
gdb/contrib/license-check-new-files.py:106:9: E722 do not use bare 'except'
...

> Tom> Add a pre-commit check check-new-file-license that runs the script.
> 
> Tom> The check is only run for new files, because it's fairly slow, about 2 seconds
> Tom> for an empty file:
> 
> Hmm that really is quite slow.  Is it 2 seconds per invocation or per
> new file?
> 

I did an experiment with 10 empty files:
...
$ for n in $(seq 1 10); do f=gdb/bla-$n.c; touch $f; git add $f; done
$ pre-commit run check-new-file-license -v
check-new-file-license...................................................Passed
- hook id: check-new-file-license
- duration: 3.18s

gdb/bla-1.c: None
gdb/bla-10.c: None
gdb/bla-2.c: None
gdb/bla-3.c: None
gdb/bla-4.c: None
gdb/bla-5.c: None
gdb/bla-6.c: None
gdb/bla-7.c: None
gdb/bla-8.c: None
gdb/bla-9.c: None
...

So, its seems it's per invocation.  If there is a significant cost per 
file we could parallelize it, the current approach is serial.

An invocation without new files is fairly quick:
...
$ pre-commit run check-new-file-license -v
check-new-file-license...................................................Passed
- hook id: check-new-file-license
- duration: 0.24s
...

> Also the script seems to run git but I wonder if that's even necessary
> in this setup.

Git is used to detect the new files using a diff command.

Maybe running this directly rather than going through a git interfacing 
library would be faster:
...
$ git diff --name-only --cached --diff-filter=A
...

Thanks,
- Tom