doc/go1.16: document BuildID in 'go list -export'

This corresponds to the feature in https://golang.org/cl/263542, since
this can be a noteworthy change to people writing tools to inspect Go
builds.

Also amend the wording to clarify that build IDs are for an entire
compiled package, not just their export data or object file.

Change-Id: I2eb295492807d5d2997a35e5e2371914cb3ad3a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/264158
Trust: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Jay Conrod <jayconrod@google.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>

4 files changed, 13 insertions, 3 deletions

diff --git a/doc/go1.16.html b/doc/go1.16.html
index 9e7ae1da27..ba2f80f95e 100644
--- a/doc/go1.16.html
+++ b/doc/go1.16.html
@@ -131,6 +131,16 @@ Do not send CLs removing the interior tags from such phrases.
   being built.
 </p>
 
+<h4 id="list-buildid">The <code>list</code> command</h4>
+
+<p><!-- golang.org/cl/263542 -->
+  When the <code>-export</code> flag is specified, the <code>BuildID</code>
+  field is now set to the build ID of the compiled package. This is equivalent
+  to running <code>go</code> <code>tool</code> <code>buildid</code> on
+  <code>go</code> <code>list</code> <code>-exported</code> <code>-f</code> <code>{{.Export}</code>,
+  but without the extra step.
+</p>
+
 <h3 id="cgo">Cgo</h3>
 
 <p> <!-- CL 252378 -->
diff --git a/src/cmd/go/alldocs.go b/src/cmd/go/alldocs.go
index 0827f0c609..23d44ddc70 100644
--- a/src/cmd/go/alldocs.go
+++ b/src/cmd/go/alldocs.go
@@ -796,7 +796,7 @@
 //         BinaryOnly    bool     // binary-only package (no longer supported)
 //         ForTest       string   // package is only for use in named test
 //         Export        string   // file containing export data (when using -export)
-//         BuildID       string   // build ID of the export data (when using -export)
+//         BuildID       string   // build ID of the compiled package (when using -export)
 //         Module        *Module  // info about package's containing module, if any (can be nil)
 //         Match         []string // command-line patterns matching this package
 //         DepOnly       bool     // package is only a dependency, not explicitly listed
diff --git a/src/cmd/go/internal/list/list.go b/src/cmd/go/internal/list/list.go
index 1c77e4d478..89088f5def 100644
--- a/src/cmd/go/internal/list/list.go
+++ b/src/cmd/go/internal/list/list.go
@@ -66,7 +66,7 @@ to -f '{{.ImportPath}}'. The struct being passed to the template is:
         BinaryOnly    bool     // binary-only package (no longer supported)
         ForTest       string   // package is only for use in named test
         Export        string   // file containing export data (when using -export)
-        BuildID       string   // build ID of the export data (when using -export)
+        BuildID       string   // build ID of the compiled package (when using -export)
         Module        *Module  // info about package's containing module, if any (can be nil)
         Match         []string // command-line patterns matching this package
         DepOnly       bool     // package is only a dependency, not explicitly listed
diff --git a/src/cmd/go/internal/load/pkg.go b/src/cmd/go/internal/load/pkg.go
index 615b5ef769..4c541b9017 100644
--- a/src/cmd/go/internal/load/pkg.go
+++ b/src/cmd/go/internal/load/pkg.go
@@ -61,7 +61,7 @@ type PackagePublic struct {
 	ConflictDir   string                `json:",omitempty"` // Dir is hidden by this other directory
 	ForTest       string                `json:",omitempty"` // package is only for use in named test
 	Export        string                `json:",omitempty"` // file containing export data (set by go list -export)
-	BuildID       string                `json:",omitempty"` // build ID of the export data (set by go list -export)
+	BuildID       string                `json:",omitempty"` // build ID of the compiled package (set by go list -export)
 	Module        *modinfo.ModulePublic `json:",omitempty"` // info about package's module, if any
 	Match         []string              `json:",omitempty"` // command-line patterns matching this package
 	Goroot        bool                  `json:",omitempty"` // is this package found in the Go root?