Make cabal update accept a freeze file

[TomMD]

Describe the bug

I want CI to build. To build we want 1) a new enough index, but we also want 2) to avoid unnecessary updates. cabal update fits the bill for the first requirement but not the second. To get both we could use a script:

timestamp=$(cat ./cabal.project.freeze | grep index-state | cut -f 3 -d ' ')
repohost=$(cat ./cabal.project.freeze | grep index-state | cut -f 2 -d ' ')
cabal v2-update ${repohost},${timestamp}

but it would be way better to call:

cabal update --project-file cabal.project.freeze

(EDITED to remove new flag and re-use an existing flag)

Would the feature be acceptable or would modifications to the design be requested?

[gbaz]

Looks like cabal update --project-file cabal.project.freeze doesn't do the trick. However, I think that fixing that interaction would make the most sense rather than adding a new flag.

[TomMD]

I didn't even know about that flag (yes, I see it in the help now). That sounds good, I'm going to edit the above ticket to say your suggestion and strike out the original text.