Update attach.md

added some clarification around why attach can appear hung to some.  issue #1456 on docs

Signed-off-by: gary schaetz <gary@schaetzkc.com>

Updated the documentation to reflect what happens when you use a fragment in
the docker build url parameter.

Signed-off-by: Gary Schaetz <gary@schaetzkc.com>

added markup for commands

Signed-off-by: Gary Schaetz <gary@schaetzkc.com>

docs/reference/commandline/attach.md

@@ -34,6 +34,11 @@ Use `docker attach` to attach your terminal's standard input, output, and error
 ID or name. This allows you to view its ongoing output or to control it
 interactively, as though the commands were running directly in your terminal.
 
+> **Note:**
+> The `attach` command will display the output of the `ENTRYPOINT/CMD` process.  This
+> can appear as if the attach command is hung when in fact the process may simply
+> not be interacting with the terminal at that time.
+
 You can attach to the same contained process multiple times simultaneously,
 even as a different user with the appropriate permissions.
 

docs/reference/commandline/build.md

@@ -80,6 +80,10 @@ the command succeeds, the directory is sent to the Docker daemon as the
 context. Local clones give you the ability to access private repositories using
 local user credentials, VPN's, and so forth.
 
+> **Note:**
+> If the `URL` parameter contains a fragment the system will recursively clone
+> the repository and its submodules using a `git clone --recursive` command.
+
 Git URLs accept context configuration in their fragment section, separated by a
 colon `:`.  The first part represents the reference that Git will check out,
 this can be either a branch, a tag, or a commit SHA. The second part represents