@@ -20,7 +20,12 @@ func ReadAll(reader io.ReadCloser) ([]string, error) {

 	var excludes []string

 	for scanner.Scan() {

-		pattern := strings.TrimSpace(scanner.Text())

+		// Lines starting with # (comments) are ignored before processing

+		pattern := scanner.Text()

+		if strings.HasPrefix(pattern, "#") {

+			continue

+		}

+		pattern = strings.TrimSpace(pattern)

 		if pattern == "" {

 			continue

 		}

@@ -379,9 +379,13 @@ the working and the root directory.  For example, the patterns

 in the `foo` subdirectory of `PATH` or in the root of the git

 repository located at `URL`.  Neither excludes anything else.

+If a line in `.dockerignore` file starts with `#` in column 1, then this line is

+considered as a comment and is ignored before interpreted by the CLI.

+

 Here is an example `.dockerignore` file:

 ```

+# comment

     */temp*

     */*/temp*

     temp?

@@ -391,6 +395,7 @@ This file causes the following build behavior:

 | Rule           | Behavior                                                                                                                                                                     |

 |----------------|------------------------------------------------------------------------------------------------------------------------------------------------------------------------------|

+| `# comment`    | Ignored.                 |

 | `*/temp*`      | Exclude files and directories whose names start with `temp` in any immediate subdirectory of the root.  For example, the plain file `/somedir/temporary.txt` is excluded, as is the directory `/somedir/temp`.                 |

 | `*/*/temp*`    | Exclude files and directories starting with `temp` from any subdirectory that is two levels below the root. For example, `/somedir/subdir/temporary.txt` is excluded. |

 | `temp?`        | Exclude files and directories in the root directory whose names are a one-character extension of `temp`.  For example, `/tempa` and `/tempb` are excluded.

@@ -6755,3 +6755,39 @@ func (s *DockerSuite) TestBuildDeleteCommittedFile(c *check.C) {

 		c.Fatal(err)

 	}

 }

+

+// #20083

+func (s *DockerSuite) TestBuildDockerignoreComment(c *check.C) {

+	name := "testbuilddockerignorecleanpaths"

+	dockerfile := `

+        FROM busybox

+        ADD . /tmp/

+        RUN sh -c "(ls -la /tmp/#1)"

+        RUN sh -c "(! ls -la /tmp/#2)"

+        RUN sh -c "(! ls /tmp/foo) && (! ls /tmp/foo2) && (ls /tmp/dir1/foo)"`

+	ctx, err := fakeContext(dockerfile, map[string]string{

+		"foo":      "foo",

+		"foo2":     "foo2",

+		"dir1/foo": "foo in dir1",

+		"#1":       "# file 1",

+		"#2":       "# file 2",

+		".dockerignore": `# Visual C++ cache files

+# because we have git ;-)

+# The above comment is from #20083

+foo

+#dir1/foo

+foo2

+# The following is considered as comment as # is at the beginning

+#1

+# The following is not considered as comment as # is not at the beginning

+  #2

+`,

+	})

+	if err != nil {

+		c.Fatal(err)

+	}

+	defer ctx.Close()

+	if _, err := buildImageFromContext(name, ctx, true); err != nil {

+		c.Fatal(err)

+	}

+}