Support `--config` options in Vitepress cli

[cocoich]

Is your feature request related to a problem? Please describe.

I need to deploy different outputs from the same source for multiple environments.
In my project, I maintain about 4 VitePress config files:

• .vitepress/config.base.mts
• .vitepress/config.prd.mts (mergeConfig with config.base.mts)
• .vitepress/config.dev.mts (mergeConfig with config.base.mts)
• .vitepress/config.prd-c.mts

Currently, in CI, I overwrite config files before running VitePress commands with ~10 lines of script.
This works, but it is fragile and hard to maintain.

Describe the solution you'd like

Please support a CLI option to specify a config file path, for example:

• vitepress dev --config .vitepress/config.dev.mts
• vitepress build --config .vitepress/config.prd.mts
• vitepress build --config .vitepress/config.prd-c.mts

This would remove the need for file overwrite steps in CI and make multi-environment workflows much simpler and safer.

Describe alternatives you've considered

• Overwriting .vitepress/config.mts in CI before each build process
• Keeping modified .vitepress/config.mts in another branch (worst)

Additional context

currently using vitepress@2.0.0-alpha.17

Found related:

• How can I change default config path, like /projectRoot/config/vitepress.config.ts. #2084

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