`lastUpdated` option causes performance degradation about starlight HOT 1 CLOSED

Looks like the related code is: https://github.com/withastro/starlight/blob/main/packages/starlight/utils/git.ts#L30 and https://github.com/withastro/starlight/blob/main/packages/starlight/utils/route-data.ts#L72

Starlight is performing a lookup with a subprocess call to git to get the last commit date for the file. Perhaps there may be a way to speed this up. Some likely naïve ideas:

• Create a cache when performing a build so we can lookup all the values at once, rather than performing individual sub-processes for each path/doc.
• Don't perform a check to see if git exists, every time we want to get the lastUpdated date for a file. (Although I guess this could be a bad idea if someone is installing/uninstalling git whilst running their dev server. Extremely unlikely though. https://github.com/withastro/starlight/blob/main/packages/starlight/utils/git.ts#L38 Actually as we're just throwing the results away, I think lines 37-53 can be removed? The call on line 55 will fail, saying either git isn't installed, or the file can't be found anyways as we're ignoring the output of the previous checks.

from starlight.