I tried before to make relative imports work by simply
invoking the compiler in the right directory, so that
an import of ./foo could be resolved by ./foo.a.
This required creating a separate tree of package binaries
that included the full path to the source directory, so that
/home/gopher/bar.go would be compiled in
tmpdir/work/local/home/gopher and perhaps find
a ./foo.a in that directory.

This model breaks on Windows because : appears in path
names but cannot be used in subdirectory names, and I
missed one or two places where it needed to be removed.

The model breaks more fundamentally when compiling
a test of a package that lives outside the Go path, because
we effectively use a ./ import in the generated testmain,
but there we want to be able to resolve the ./ import
of the test package to one directory and all the other ./
imports to a different directory.  Piggybacking on the compiler's
current working directory is then no longer possible.

Instead, introduce a new compiler option -D prefix that
makes the compiler turn a ./ import into prefix+that,
so that import "./foo" with -D a/b/c turns into import
"a/b/c/foo".  Then we can invent a package hierarchy
"_/" with subdirectories named for file system paths:
import "./foo" in the directory /home/gopher becomes
import "_/home/gopher/foo", and since that final path
is just an ordinary import now, all the ordinary processing
works, without special cases.

We will have to change the name of the hierarchy if we
ever decide to introduce a standard package with import
path "_", but that seems unlikely, and the detail is known
only in temporary packages that get thrown away at the
end of a build.

Fixes #3169.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5732045

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5726047

R=golang-dev
CC=golang-dev
https://golang.org/cl/5728050

R=golang-dev, minux.ma, rsc
CC=golang-dev, remy
https://golang.org/cl/5699079

Make some updates, get rid of mentions of make.
There remain a number of open questions.

R=golang-dev, gri
CC=golang-dev
https://golang.org/cl/5720057

- makes space for Xcode4 files
- added README

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5720059

R=rsc, golang-dev, iant
CC=golang-dev
https://golang.org/cl/5732043

        Dynamically allocate the libdir array, so we won't need to bother it again.
        Enhances CL 5727043.

R=rsc
CC=golang-dev
https://golang.org/cl/5731043

Except for the tests, this is mostly deleting code:

- removed several exprListModes:
  blankStart: easily done explicitly, and trailing blanks
    are cleaned up by the trimmer post-pass
  blankEnd: never used
  commaSep: all exprLists calls had this set

- added test cases for multi-line returns
(for a later fix of issue 1207)

- no formatting changes

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5672062

R=golang-dev, bradfitz, r
CC=golang-dev
https://golang.org/cl/5720044

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5716053

        Set dagger looks very much like t in some fonts, so superscript it.
        os/signal is no longer in exp.

R=golang-dev, adg
CC=golang-dev
https://golang.org/cl/5720049

Fixes #3171.

R=golang-dev, rsc
CC=golang-dev, remy
https://golang.org/cl/5724045

R=golang-dev, rsc
CC=adg, golang-dev
https://golang.org/cl/5720050

Fixes a problem Rob is having with goprotobuf.
Cannot add a test because the same case is more broken
when using ./ imports.  That still needs to be fixed,
and is one aspect of issue 3169.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5725043

Also remove useless "install" argument to pkgpath now that go/build
defines package install locations.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5714059

Build environments will often define stock LDFLAGS
that are not compatible with the gc ld, causing
non-obvious failures midway through the build.

R=golang-dev, rsc, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/5724044

Fixes #2866.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5719047

R=golang-dev, balasanjay, r
CC=golang-dev
https://golang.org/cl/5640045

Fixes #3145.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5721044

Asymptotic convergence.

R=golang-dev, dsymonds
CC=golang-dev
https://golang.org/cl/5719045

Also change Wait to say "exit" instead of "exit or stop".

I notice that Pid is not implemented on all systems.
Should we fix that?

Fixes #3138.

R=golang-dev, alex.brainman, r
CC=golang-dev
https://golang.org/cl/5710056

R=golang-dev, rsc, r
CC=golang-dev
https://golang.org/cl/5713054

Presumably something about the very large go/build
doc comment breaks the build constraint parser in
cmd/dist.  I don't feel like debugging C code right now,
so move it into its own file.  If cmd/dist decides doc.go
is not part of the package, it will still build correctly.

R=golang-dev
TBR=golang-dev
CC=golang-dev
https://golang.org/cl/5722043

Fixes #2332.

R=golang-dev, remyoudompheng, gri, r, r
CC=golang-dev
https://golang.org/cl/5710055

R=golang-dev, gri, r
CC=golang-dev
https://golang.org/cl/5711059

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5715050

R=rsc, remyoudompheng
CC=golang-dev
https://golang.org/cl/5711056

(Semi-automatically detected.)

R=golang-dev, remyoudompheng, r
CC=golang-dev
https://golang.org/cl/5715052

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5716057

- Define what it means for two identifiers to be unique.

- The current spec is incorrect about exported
identifiers: for instance, it excluded fields
of non-exported types of exported variables
from being exported. It is easier to leave
the detailed specification away and let the
rest of the spec govern access of exported
identifiers.

- The current spec is incorrect about qualified
identifiers: It simply required that an identifier
be exported to be valid in a qualified identifier.
However, qualified identifiers can only access
exported identifiers declared in the package
block of the imported package.

Fixes #1551.

R=r, rsc, iant, ken
CC=golang-dev
https://golang.org/cl/5711043

Fixes #3165.

R=golang-dev, iant
CC=golang-dev
https://golang.org/cl/5712051

- more idiomatic examples of pointer types
- show use of _ in examples of function types
- remove "legal:" qualification in examples
  for consistency

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5711054

No real problem.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5717049

R=golang-dev, rsc, bradfitz
CC=golang-dev
https://golang.org/cl/5715046

The docs look awkward - there is a paragraph
"For example:" with a plain text example,
and straight below it a real Example.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/5717048

* Install tools into tool dir always
  (Fixes issue 3049.  Fixes issue 2868.  Fixes issue 2925.)
* Make packages depend on compiler, linker (Fixes issue 3036.)
* Do not recompile packages across roots (Fixes issue 3149.)
* Allow use of binary-only packages (Fixes issue 2775.)
* Avoid duplicate cgo dependencies (Fixes issue 3001.)
* Show less in go get -x.  (Fixes issue 2926.)
* Do not force repo root for existing checkout (Fixes issue 2969.)
* Show full syntax error list always (Fixes issue 2811.)
* Clean arguments before processing (Fixes issue 3034.)
* Add flags for compiler, linker arguments (Fixes issue 2996.)
* Pass flags in make.bash (Fixes issue 3091.)
* Unify build flags, defined in one place.
* Clean up error messages (Fixes issue 3075.  Fixes issue 2923.)
* Support local import paths (Fixes issue 3118.)
* Allow top-level package outside $GOPATH (Fixes issue 3009.)

In addition to these fixes, all commands now take a list of
go files as a way to specify a single package, just as go build and
go run always have.  This means you can:

        go list -json x.go
        go fix x.go
        go vet x.go
        go test x_test.go

Preliminary tests in test.bash.
Mainly testing things that the ordinary build does not.
I don't mind if the script doesn't run on Windows.

I expect that gccgo support is now broken, and I hope that
people will feel free to file issues and/or send CLs to fix it.  :-)

R=golang-dev, dsymonds, r, rogpeppe
CC=golang-dev
https://golang.org/cl/5708054

This is an API change, but one I have been promising would
happen when it was clear what the go command needed.

This is basically a complete replacement of what used to be here.

build.Tree is gone.

build.DirInfo is expanded and now called build.Package.

build.FindTree is now build.Import(package, srcDir, build.FindOnly).
The returned *Package contains information that FindTree returned,
but applicable only to a single package.

build.ScanDir is now build.ImportDir.

build.FindTree+build.ScanDir is now build.Import.

The new Import API allows specifying the source directory,
in order to resolve local imports (import "./foo") and also allows
scanning of packages outside of $GOPATH.  They will come back
with less information in the Package, but they will still work.

The old go/build API exposed both too much and too little.
This API is much closer to what the go command needs,
and it works well enough in the other places where it is
used.  Path is gone, so it can no longer be misused.  (Fixes issue 2749.)

This CL updates clients of go/build other than the go command.
The go command changes are in a separate CL, to be submitted
at the same time.

R=golang-dev, r, alex.brainman, adg
CC=golang-dev
https://golang.org/cl/5713043

Fixes #3134.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5713049

Fixes #3125.

R=golang-dev, r, minux.ma
CC=golang-dev
https://golang.org/cl/5714049