benchseries: make this package public but mark it unstable

benchseries' API is currently unstable, so it lives in an internal
directory. However, after CL 395175, we're going to want x/build to
depend on it.

This change moves this package outside of the internal directory, but
also adds package documentation marking the API as experimental and
unstable.

For golang/go#48803.

Change-Id: I5811d8f27bfbaa4cdd0e116adccaad5d43c2bcff
Reviewed-on: https://go-review.googlesource.com/c/perf/+/395654
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: David Chase <drchase@google.com>
diff --git a/internal/benchseries/benchseries.go b/benchseries/benchseries.go
similarity index 100%
rename from internal/benchseries/benchseries.go
rename to benchseries/benchseries.go
diff --git a/internal/benchseries/chart.go b/benchseries/chart.go
similarity index 100%
rename from internal/benchseries/chart.go
rename to benchseries/chart.go
diff --git a/internal/benchseries/csv.go b/benchseries/csv.go
similarity index 100%
rename from internal/benchseries/csv.go
rename to benchseries/csv.go
diff --git a/benchseries/doc.go b/benchseries/doc.go
new file mode 100644
index 0000000..b330701
--- /dev/null
+++ b/benchseries/doc.go
@@ -0,0 +1,9 @@
+// Copyright 2022 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.
+
+// The benchseries package generates performance differentials and analysis tailored
+// to the output of tools and benchmarks in golang.org/x/benchmarks.
+//
+// WARNING: The API is experimental, unstable, and subject to change at any time.
+package benchseries
diff --git a/cmd/benchseries/main.go b/cmd/benchseries/main.go
index ee3e4e1..b8e787b 100644
--- a/cmd/benchseries/main.go
+++ b/cmd/benchseries/main.go
@@ -12,7 +12,7 @@
 
 	// "github.com/dr2chase/debug-server/debug_client"
 	"golang.org/x/perf/benchfmt"
-	"golang.org/x/perf/internal/benchseries"
+	"golang.org/x/perf/benchseries"
 	// "runtime"
 )
 
diff --git a/cmd/benchseries/main_test.go b/cmd/benchseries/main_test.go
index 7603082..2cd3e47 100644
--- a/cmd/benchseries/main_test.go
+++ b/cmd/benchseries/main_test.go
@@ -16,7 +16,7 @@
 	"testing"
 
 	"golang.org/x/perf/benchfmt"
-	"golang.org/x/perf/internal/benchseries"
+	"golang.org/x/perf/benchseries"
 )
 
 var bo *benchseries.BuilderOptions