net/http: http.Client don't use original Header when it do redirect

[gopherbot]

by yunge.fu:

When http.Client receives http redirect response, it just copy part of origin Headers,
such as "Referer", for the new Request.
But sometimes people need original or custom Headers, such as UserAgent, by now
http.Client will always use defaultUserAgent.

I think just copy the original Header for the new Request is a better way.

The related code is in:
http://golang.org/src/pkg/net/http/client.go, func doFollowingRedirects()

[gopherbot]

Comment 1 by yunge.fu:

Sorry, I should say the http.Client just ignore the original Header when it follow
redirection.

[ianlancetaylor]

Comment 2:

Labels changed: added repo-main, release-none.

[bradfitz]

Comment 3:

Status changed to Duplicate.

Merged into issue #4800.