http: improve TokenAuth documentation

Users are often confused with TokenAuth, since it might look that it
should be used with GitHub's OAuth tokens. But that is not the case.

TokenAuth implements HTTP bearer authentication. Most git servers will
use HTTP basic authentication (user+passwords) even for OAuth tokens.

Signed-off-by: Santiago M. Mola <[email protected]>

plumbing/transport/http/common.go

@@ -214,7 +214,14 @@ func (a *BasicAuth) String() string {
 	return fmt.Sprintf("%s - %s:%s", a.Name(), a.Username, masked)
 }
 
-// TokenAuth implements the go-git http.AuthMethod and transport.AuthMethod interfaces
+// TokenAuth implements an http.AuthMethod that can be used with http transport
+// to authenticate with HTTP token authentication (also known as bearer
+// authentication).
+//
+// IMPORTANT: If you are looking to use OAuth tokens with popular servers (e.g.
+// GitHub, Bitbucket, GitLab) you should use BasicAuth instead. These servers
+// use basic HTTP authentication, with the OAuth token as user or password.
+// Check the documentation of your git server for details.
 type TokenAuth struct {
 	Token string
 }