unix: factor out mkmerge into a proper package

Factor mkmerge.go and mkmerge_test.go into package internal/mkmerge.

Due to ignore constraints, mkmerge_test.go wasn't run by the Go
builders and failing tests were unnoticed.

Factoring mkmerge into its own package and removing ignore constraints
makes the tests run automatically by the Go builders.

Fixes golang/go#49484

Change-Id: I56a0b7220e40d1d7e5193490cb547cad4202f9ac
Reviewed-on: https://go-review.googlesource.com/c/sys/+/363334
Run-TryBot: Tobias Klauser <tobias.klauser@gmail.com>
Reviewed-by: Bryan C. Mills <bcmills@google.com>
Reviewed-by: Tobias Klauser <tobias.klauser@gmail.com>
Trust: Bryan C. Mills <bcmills@google.com>
TryBot-Result: Go Bot <gobot@golang.org>

unix/README.md

@@ -149,7 +149,7 @@ To add a constant, add the header that includes it to the appropriate variable.
 Then, edit the regex (if necessary) to match the desired constant. Avoid making
 the regex too broad to avoid matching unintended constants.
 
-### mkmerge.go
+### internal/mkmerge
 
 This program is used to extract duplicate const, func, and type declarations
 from the generated architecture-specific files listed below, and merge these

unix/internal/mkmerge/mkmerge.go

@@ -2,25 +2,22 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build ignore
-// +build ignore
-
-// mkmerge.go parses generated source files and merges common
+// The mkmerge command parses generated source files and merges common
 // consts, funcs, and types into a common source file, per GOOS.
 //
 // Usage:
-//     $ go run mkmerge.go -out MERGED FILE [FILE ...]
+//     $ mkmerge -out MERGED FILE [FILE ...]
 //
 // Example:
 //     # Remove all common consts, funcs, and types from zerrors_linux_*.go
 //     # and write the common code into zerrors_linux.go
-//     $ go run mkmerge.go -out zerrors_linux.go zerrors_linux_*.go
+//     $ mkmerge -out zerrors_linux.go zerrors_linux_*.go
 //
-// mkmerge.go performs the merge in the following steps:
-// 1. Construct the set of common code that is idential in all
-//    architecture-specific files.
-// 2. Write this common code to the merged file.
-// 3. Remove the common code from all architecture-specific files.
+// mkmerge performs the merge in the following steps:
+//     1. Construct the set of common code that is idential in all
+//        architecture-specific files.
+//     2. Write this common code to the merged file.
+//     3. Remove the common code from all architecture-specific files.
 package main
 
 import (
@@ -464,7 +461,7 @@ func merge(mergedFile string, archFiles ...string) error {
 	}
 
 	buf := bufio.NewWriter(f)
-	fmt.Fprintln(buf, "// Code generated by mkmerge.go; DO NOT EDIT.")
+	fmt.Fprintln(buf, "// Code generated by mkmerge; DO NOT EDIT.")
 	fmt.Fprintln(buf)
 	fmt.Fprintf(buf, "//go:build %s\n", goos)
 	fmt.Fprintf(buf, "// +build %s\n", goos)

unix/internal/mkmerge/mkmerge_test.go

@@ -2,12 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build ignore
-// +build ignore
-
-// Test cases for mkmerge.go.
-// Usage:
-//     $ go test mkmerge.go mkmerge_test.go
 package main
 
 import (

unix/linux/mkall.go

@@ -572,7 +572,7 @@ func mergeFiles() error {
 
 	// Merge each of the four type of files
 	for _, ztyp := range []string{"zerrors", "zsyscall", "zsysnum", "ztypes"} {
-		cmd := makeCommand("go", "run", "mkmerge.go", "-out", fmt.Sprintf("%s_%s.go", ztyp, GOOS), fmt.Sprintf("%s_%s_*.go", ztyp, GOOS))
+		cmd := makeCommand("go", "run", "./internal/mkmerge", "-out", fmt.Sprintf("%s_%s.go", ztyp, GOOS), fmt.Sprintf("%s_%s_*.go", ztyp, GOOS))
 		err := cmd.Run()
 		if err != nil {
 			return fmt.Errorf("could not merge %s files: %w", ztyp, err)

unix/zerrors_linux.go

@@ -1,4 +1,4 @@
-// Code generated by mkmerge.go; DO NOT EDIT.
+// Code generated by mkmerge; DO NOT EDIT.
 
 //go:build linux
 // +build linux

unix/zsyscall_linux.go

@@ -1,4 +1,4 @@
-// Code generated by mkmerge.go; DO NOT EDIT.
+// Code generated by mkmerge; DO NOT EDIT.
 
 //go:build linux
 // +build linux

unix/ztypes_linux.go

@@ -1,4 +1,4 @@
-// Code generated by mkmerge.go; DO NOT EDIT.
+// Code generated by mkmerge; DO NOT EDIT.
 
 //go:build linux
 // +build linux