cmd/bent: remove outdated references to rsync and cp

Since CL 617555 rsync exec's were replaced with sweet's copyDir.
This removes misleading mentions of rsync and cp.

Change-Id: I78ffbac2683f80b6c6c3a17c653a01e50c831c89
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/674395
Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>

cmd/bent/README.md

diff --git a/cmd/bent/README.md b/cmd/bent/README.md
index 55030e8..7732ce9 100644
--- a/cmd/bent/README.md
+++ b/cmd/bent/README.md
@@ -13,8 +13,6 @@
 
 Depends on burntsushi/toml.
 
-Install `rsync` for slightly improved copy performance.
-
 Initial usage :
 
 ```

cmd/bent/bent.go

diff --git a/cmd/bent/bent.go b/cmd/bent/bent.go
index 69b80af..77dbf8f 100644
--- a/cmd/bent/bent.go
+++ b/cmd/bent/bent.go
@@ -677,7 +677,7 @@
 			docopy := func(from, to string) {
 				fileutil.CopyDir(to, from, nil)
 				if verbose > 0 || err != nil {
-					fmt.Printf("rsync -a %s %s, error=%v\n", from, to, err)
+					fmt.Printf("Copying directory %s to %s, error=%v\n", from, to, err)
 				}
 			}
 
@@ -917,12 +917,12 @@
 					os.Mkdir(testdataCopy, fs.FileMode(0755))
 					err = fileutil.CopyDir(testdataCopy, testdata, nil)
 					if verbose > 0 || err != nil {
-						commandLine = fmt.Sprintf("rsync -a %s/ %s", testdata, testdataCopy)
+						commandLine = fmt.Sprintf("Copying directory %s %s", testdata, testdataCopy)
 					}
 				} else {
 					err = fileutil.CopyFile(testdataCopy, testdata, nil, nil)
 					if verbose > 0 || err != nil {
-						commandLine = fmt.Sprintf("cp -p %s %s", testdata, testdataCopy)
+						commandLine = fmt.Sprintf("Copying %s to %s", testdata, testdataCopy)
 					}
 				}
 				if verbose > 0 {