The 4 functions are duplicated, especially as interface methods. I think
we just need to keep `MustID` the only one and remove other 3.
```
MustID(b []byte) ObjectID
MustIDFromString(s string) ObjectID
NewID(b []byte) (ObjectID, error)
NewIDFromString(s string) (ObjectID, error)
```
Introduced the new interfrace method `ComputeHash` which will replace
the interface `HasherInterface`. Now we don't need to keep two
interfaces.
Reintroduced `git.NewIDFromString` and `git.MustIDFromString`. The new
function will detect the hash length to decide which objectformat of it.
If it's 40, then it's SHA1. If it's 64, then it's SHA256. This will be
right if the commitID is a full one. So the parameter should be always a
full commit id.
@AdamMajer Please review.
Refactor Hash interfaces and centralize hash function. This will allow
easier introduction of different hash function later on.
This forms the "no-op" part of the SHA256 enablement patch.
There are too many files under `routers/web/repo` and the file
`routers/web/repo/setting.go` is too big.
This PR move all setting related routers' body functions under
`routers/web/repo/setting` and also split `routers/web/repo/setting.go`
Lunny Xiao