mcp: add log and diff tools

[aluzzardi]

• Add environment log and diff tools via MCP
• Add -b flag to cu {log,diff}

[cwlbraa]

in raw git, isn't this equivalent to git diff main fancy-mallard? or git diff fancy-mallard main we should make sure we're copying that UX wherever possible.

also why does it say backend-api, those are adverb animals lol

[aluzzardi]

cu diff is slightly different than a git diff ... out of the box, it does a git diff $(git merge-base $(git branch --show-current) CU_ENV))..CU_ENV

The -b here is replacing the merge-base stuff with whatever is in -b

Really unsure whether we should copy the syntax or not here, especially since I think we'll want to support paths (like git) and the syntax gets tricky

git diff main fancy-mallard
git diff main..fancy-mallard
git diff main..fancy-mallard ./cmd
git diff main fancy-mallard -- ./cmd

[aluzzardi]

Any opinion from a git UX POV?