Tool to remove unused identifiers from go-packages

This was my entry to 5th go challenge (http://golang-challenge.com)

unexport searches unnecessarily exported identifiers from a package. Identifiers are declared unnecessarily exported, if no-one outside the declaring package is using them. This can't be 100% guaranteed for other than "internal"-packages, so by default only "internal"-packages can be unexported.

Unexport candidates are provided as "gorename"-commands. Possible naming collisions caused by unexporting are also reported.

unexport -pkg <target-package> [-search <search-from-package>] [-unsafe] [-offset] [-help] [-report]

Flags:

• -help: print this help
• -offset: use 'file offset'-notation instead of 'from'-notation for gorename
• -pkg <string>: go package to unexport
• -report: show which exported identifiers are used and by whom
• -search <string>: search usage of exported identifiers from this package (and its subpackages) NOTE: If this has not been specified, whole $GOPATH will be searched (and it might take a while).
• -unsafe: allow unexporting other than internal packages

unexport -pkg cmd/compile/internal/gc

unexport -pkg cmd/compile/internal/gc -search cmd/compile/internal/big

unexport -pkg cmd/compile/internal/gc -report

unexport -pkg cmd/vet -search cmd/fix -unsafe -offset