introduce a binary grep command for the tests

The problem with the "grep" built-in command is that it prints the
entire data if there is an error. We don't want megabytes of binary
output for a test.

main_test.go

@@ -8,6 +8,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"regexp"
 	"testing"
 
 	"github.com/rogpeppe/go-internal/testscript"
@@ -48,6 +49,26 @@ func TestScripts(t *testing.T) {
 			}
 			return nil
 		},
+		Cmds: map[string]func(ts *testscript.TestScript, neg bool, args []string){
+			"bingrep": bingrep,
+		},
 		UpdateScripts: *update,
 	})
 }
+
+func bingrep(ts *testscript.TestScript, neg bool, args []string) {
+	if len(args) < 2 {
+		ts.Fatalf("usage: bingrep file pattern...")
+	}
+	data := ts.ReadFile(args[0])
+	for _, pattern := range args[1:] {
+		rx, err := regexp.Compile(pattern)
+		ts.Check(err)
+		match := rx.MatchString(data)
+		if match && neg {
+			ts.Fatalf("unexpected match for %q in %s", pattern, args[0])
+		} else if !match && !neg {
+			ts.Fatalf("expected match for %q in %s", pattern, args[0])
+		}
+	}
+}

testdata/scripts/basic.txt

@@ -4,15 +4,14 @@
 exec go build main.go
 exec ./main
 cmp stderr main.stderr
-grep $WORK main
 
 # The default build includes DWARF and the symbol table.
 exec readelf --section-headers main
 stdout 'debug_info'
 stdout '\.symtab'
 
-# The default build includes full non-trimmed paths.
-grep $WORK main
+# The default build includes full non-trimmed paths, as well as our names.
+bingrep main$exe ${WORK@R} 'globalVar' 'globalFunc'
 
 # Check that we fail if the user forgot -trimpath.
 ! exec go build -a -toolexec=garble main.go
@@ -27,15 +26,13 @@ exec readelf --section-headers main
 ! stdout 'debug_info'
 ! stdout '\.symtab'
 
-! grep $WORK main
-! grep 'globalVar' main
-! grep 'globalFunc' main
+! bingrep main$exe ${WORK@R} 'globalVar' 'globalFunc'
 
 # Finally, check that the 'garble build' shortcut works.
 # cp main main_old
 garble build main.go
-! grep 'globalVar' main
-# cmp main main_old
+! bingrep main$exe 'globalVar'
+# bincmp main main_old
 
 -- main.go --
 package main

testdata/scripts/implement.txt

@@ -2,7 +2,7 @@ garble build main.go
 exec ./main
 cmp stdout main.stdout
 
-! grep 'unexportedMethod' main
+! bingrep main$exe 'unexportedMethod'
 
 -- main.go --
 package main

testdata/scripts/imports.txt

@@ -2,10 +2,7 @@ garble build
 exec ./main
 cmp stdout main.stdout
 
-! grep 'ImportedVar' main
-! grep 'ImportedConst' main
-! grep 'ImportedFunc' main
-! grep 'ImportedType' main
+! bingrep main$exe 'ImportedVar' 'ImportedConst' 'ImportedFunc' 'ImportedType'
 
 -- go.mod --
 module foo.com/main

testdata/scripts/modinfo.txt

@@ -1,11 +1,12 @@
 exec go build
 exec ./main
 cmp stdout main.stdout-orig
+bingrep main$exe '\(devel\)'
 
 garble build
 exec ./main
 cmp stdout main.stdout
-! grep '\(devel\)' main
+! bingrep main$exe '\(devel\)'
 
 -- go.mod --
 module foo.com/main