// Copyright 2010 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

/*
Goinstall is an experiment in automatic package installation.
It installs packages, possibly downloading them from the internet.
It maintains a list of public Go packages at
http://godashboard.appspot.com/package.

Usage:
	goinstall [flags] importpath...
	goinstall [flags] -a

Flags and default settings:
        -a=false          install all previously installed packages
	-clean=false      clean the package directory before installing
	-dashboard=true   tally public packages on godashboard.appspot.com
	-install=true     build and install the package and its dependencies
	-nuke=false       remove the target object and clean before installing
	-u=false          update already-downloaded packages
	-v=false          verbose operation

Goinstall installs each of the packages identified on the command line.  It
installs a package's prerequisites before trying to install the package
itself. Unless -log=false is specified, goinstall logs the import path of each
installed package to $GOROOT/goinstall.log for use by goinstall -a.

If the -a flag is given, goinstall reinstalls all previously installed
packages, reading the list from $GOROOT/goinstall.log.  After updating to a
new Go release, which deletes all package binaries, running

	goinstall -a

will recompile and reinstall goinstalled packages.

Another common idiom is to use

	goinstall -a -u

to update, recompile, and reinstall all goinstalled packages.

The source code for a package with import path foo/bar is expected
to be in the directory $GOROOT/src/pkg/foo/bar/ or $GOPATH/src/foo/bar/.
See "The GOPATH Environment Variable" for more about GOPATH.

By default, goinstall prints output only when it encounters an error.
The -v flag causes goinstall to print information about packages
being considered and installed.

Goinstall ignores Makefiles.


Remote Repositories

If a package import path refers to a remote repository, goinstall will
download the code if necessary.

Goinstall recognizes packages from a few common code hosting sites:

	BitBucket (Git, Mercurial)

		import "bitbucket.org/user/project"
		import "bitbucket.org/user/project/sub/directory"

	GitHub (Git)

		import "github.com/user/project"
		import "github.com/user/project/sub/directory"

	Google Code Project Hosting (Git, Mercurial, Subversion)

		import "project.googlecode.com/git"
		import "project.googlecode.com/git/sub/directory"

		import "project.googlecode.com/hg"
		import "project.googlecode.com/hg/sub/directory"

		import "project.googlecode.com/svn/trunk"
		import "project.googlecode.com/svn/trunk/sub/directory"

	Google Code Project Hosting sub-repositories:

		import "code.google.com/p/project.subrepo/sub/directory

	Launchpad (Bazaar)

		import "launchpad.net/project"
		import "launchpad.net/project/series"
		import "launchpad.net/project/series/sub/directory"

		import "launchpad.net/~user/project/branch"
		import "launchpad.net/~user/project/branch/sub/directory"

If the destination directory (e.g., $GOROOT/src/pkg/bitbucket.org/user/project)
already exists and contains an appropriate checkout, goinstall will not
attempt to fetch updates.  The -u flag changes this behavior,
causing goinstall to update all remote packages encountered during
the installation.

When downloading or updating, goinstall looks for a tag with the "go." prefix
that corresponds to the local Go version. For Go "release.r58" it looks for a
tag named "go.r58". For "weekly.2011-06-03" it looks for "go.weekly.2011-06-03".
If the specific "go.X" tag is not found, it chooses the closest earlier version.
If an appropriate tag is found, goinstall uses that version of the code.
Otherwise it uses the default version selected by the version control
system, typically HEAD for git, tip for Mercurial.

After a successful download and installation of one of these import paths,
goinstall reports the installation to godashboard.appspot.com, which
increments a count associated with the package and the time of its most
recent installation. This mechanism powers the package list at
http://godashboard.appspot.com/package, allowing Go programmers to learn about
popular packages that might be worth looking at.	 
The -dashboard=false flag disables this reporting.

For code hosted on other servers, goinstall recognizes the general form

	repository.vcs/path

as denoting the given repository, with or without the .vcs suffix, using
the named version control system, and then the path inside that repository.
The supported version control systems are:

	Bazaar      .bzr
	Git         .git
	Mercurial   .hg
	Subversion  .svn

For example, 

	import "example.org/user/foo.hg"

denotes the root directory of the Mercurial repository at example.org/user/foo
or foo.hg, and

	import "example.org/repo.git/foo/bar"

denotes the foo/bar directory of the Git repository at example.com/repo or
repo.git.

When a version control system supports multiple protocols, goinstall tries each
in turn.
For example, for Git it tries git://, then https://, then http://.


The GOPATH Environment Variable

GOPATH may be set to a colon-separated list of paths inside which Go code,
package objects, and executables may be found.

Set a GOPATH to use goinstall to build and install your own code and
external libraries outside of the Go tree (and to avoid writing Makefiles).

The top-level directory structure of a GOPATH is prescribed:

The 'src' directory is for source code. The directory naming inside 'src'
determines the package import path or executable name.

The 'pkg' directory is for package objects. Like the Go tree, package objects
are stored inside a directory named after the target operating system and
processor architecture ('pkg/$GOOS_$GOARCH').
A package whose source is located at '$GOPATH/src/foo/bar' would be imported
as 'foo/bar' and installed as '$GOPATH/pkg/$GOOS_$GOARCH/foo/bar.a'.

The 'bin' directory is for executable files.
Goinstall installs program binaries using the name of the source folder.
A binary whose source is at 'src/foo/qux' would be built and installed to
'$GOPATH/bin/qux'. (Note 'bin/qux', not 'bin/foo/qux' - this is such that
you can put the bin directory in your PATH.) 

Here's an example directory layout:

	GOPATH=/home/user/gocode

	/home/user/gocode/
		src/foo/
			bar/               (go code in package bar)
			qux/               (go code in package main)
		bin/qux                    (executable file)
		pkg/linux_amd64/foo/bar.a  (object file)

Run 'goinstall foo/bar' to build and install the package 'foo/bar'
(and its dependencies).
Goinstall will search each GOPATH (in order) for 'src/foo/bar'.
If the directory cannot be found, goinstall will attempt to fetch the
source from a remote repository and write it to the 'src' directory of the
first GOPATH (or $GOROOT/src/pkg if GOPATH is not set).

Goinstall recognizes relative and absolute paths (paths beginning with / or .).
The following commands would build our example packages:

	goinstall /home/user/gocode/src/foo/bar  # build and install foo/bar
	cd /home/user/gocode/src/foo
	goinstall ./bar  # build and install foo/bar (again)
	cd qux
	goinstall .      # build and install foo/qux

*/
package documentation