man: prevent cobra "source" comment

Cobra sets a default Source if none is set;

    header.Source = "Auto generated by spf13/cobra"

Set our own Source for the man pages we generate.

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

Author: thaJeztah

clidocstool_man.go

@@ -41,7 +41,9 @@ func (c *Client) GenManTree(cmd *cobra.Command) error {
 		now := time.Unix(unixEpoch, 0)
 		c.manHeader.Date = &now
 	}
-
+	if c.manHeader.Source == "" {
+		c.manHeader.Source = "Generated by github.com/docker/cli-docs-tool"
+	}
 	return c.genManTreeCustom(cmd)
 }