x/tools/cmd/godoc: show which version of Go introduced symbols

[ncw]

Go documentation is very good, but it doesn't clearly label which go version features
are available in.

For instance I was caught out by http://golang.org/pkg/time/#Timer.Reset being a go 1.1
feature which meant my code would no longer compile with go 1.0.

Other examples are 

  * http://golang.org/pkg/net/http/#Transport.CancelRequest
  * ResponseHeaderTimeout in http://golang.org/pkg/net/http/#Transport

[adg]

Comment 1:

How did it catch you out? Why can't you just update the 1.0-based systems to 1.1?

Status changed to Thinking.

[ncw]

Comment 2:

I was updating a public library and I don't want to break 1.0 compatibility for my users
just yet, but I managed to do that by accident!

[ianlancetaylor]

Comment 3:

The additions are noted at http://golang.org/doc/go1.1 , but it's true that it might be
useful to also note them in the individual docs.  Or perhaps we can have go api check
status of code.

[rsc]

Comment 4:

Maybe godoc should read $GOROOT/api/go1.1.txt.

[rsc]

Comment 5:

Labels changed: added priority-later, go1.2maybe, removed priority-triage.

[rsc]

Comment 6:

Labels changed: added documentation.

[rsc]

Comment 7:

Probably too big for now.

Labels changed: added go1.3, removed go1.2maybe.

[rsc]

Comment 8:

Labels changed: added release-go1.3, removed go1.3.

[rsc]

Comment 9:

Labels changed: added repo-main.

[rsc]

Comment 10:

Labels changed: added release-none, removed release-go1.3.

[pierrre]

Comment 11:

In Android doc: http://developer.android.com/reference/packages.html
you can filter by API level.

[ianlancetaylor]

Comment 12:

Issue #8468 has been merged into this issue.