pkg/kernel: allow to split full make output

Currently kernel build failures are insanely verbose
(contain full kernel build output) and there is no
way to separate short descriptions from full output.
Make it possible.
Also try to extract failure root cause froom build log.
Use this in pkg/bisect to not pollute log on build failures.

Update #501

1 files changed, 23 insertions, 2 deletions

diff --git a/pkg/osutil/osutil.go b/pkg/osutil/osutil.go
index a1d65e835..e41ad7ec1 100644
--- a/pkg/osutil/osutil.go
+++ b/pkg/osutil/osutil.go
@@ -47,8 +47,10 @@ func Run(timeout time.Duration, cmd *exec.Cmd) ([]byte, error) {
 	}()
 	defer close(done)
 	if err := cmd.Wait(); err != nil {
-		return nil, fmt.Errorf("failed to run %v %+v: %v\n%v",
-			cmd.Path, cmd.Args, err, output.String())
+		return nil, &VerboseError{
+			Title:  fmt.Sprintf("failed to run %v %+v: %v", cmd.Path, cmd.Args, err),
+			Output: output.Bytes(),
+		}
 	}
 	return output.Bytes(), nil
 }
@@ -60,6 +62,25 @@ func Command(bin string, args ...string) *exec.Cmd {
 	return cmd
 }
 
+type VerboseError struct {
+	Title  string
+	Output []byte
+}
+
+func (err *VerboseError) Error() string {
+	return fmt.Sprintf("%v\n%s", err.Title, err.Output)
+}
+
+func PrependContext(ctx string, err error) error {
+	switch err1 := err.(type) {
+	case *VerboseError:
+		err1.Title = fmt.Sprintf("%v: %v", ctx, err1.Title)
+		return err1
+	default:
+		return fmt.Errorf("%v: %v", ctx, err)
+	}
+}
+
 // IsExist returns true if the file name exists.
 func IsExist(name string) bool {
 	_, err := os.Stat(name)