Add test cases and docString for regex in COPY command (#2773)

pkg/commands/copy.go

@@ -58,6 +58,7 @@ func (c *CopyCommand) ExecuteCommand(config *v1.Config, buildArgs *dockerfile.Bu
 		return errors.Wrap(err, "getting user group from chown")
 	}
 
+	// sources from the Copy command are resolved with wildcards {*?[}
 	srcs, dest, err := util.ResolveEnvAndWildcards(c.cmd.SourcesAndDest, c.fileContext, replacementEnvs)
 	if err != nil {
 		return errors.Wrap(err, "resolving src")

pkg/commands/copy_test.go

@@ -51,6 +51,21 @@ var copyTests = []struct {
 		sourcesAndDest: []string{"foo", "tempCopyExecuteTest"},
 		expectedDest:   []string{"tempCopyExecuteTest"},
 	},
+	{
+		name:           "copy f* into tempCopyExecuteTest",
+		sourcesAndDest: []string{"foo*", "tempCopyExecuteTest"},
+		expectedDest:   []string{"tempCopyExecuteTest"},
+	},
+	{
+		name:           "copy fo? into tempCopyExecuteTest",
+		sourcesAndDest: []string{"fo?", "tempCopyExecuteTest"},
+		expectedDest:   []string{"tempCopyExecuteTest"},
+	},
+	{
+		name:           "copy f[o][osp] into tempCopyExecuteTest",
+		sourcesAndDest: []string{"f[o][osp]", "tempCopyExecuteTest"},
+		expectedDest:   []string{"tempCopyExecuteTest"},
+	},
 }
 
 func setupTestTemp(t *testing.T) string {