Fix long option format on docs.podman.io

Escape the two dashes, otherwise they are combined into one long dash.
I tested that this change is safe and still renders correctly on github
and with the man pages.

This commit also contains a small change to make it build locally.
Assuming you have the dependencies installed you can do:
```
cd docs
make html
```
Preview the html files in docs/build/html with
`python -m http.server 8000 --directory build/html`.

Fixes containers/podman.io#373

Signed-off-by: Paul Holzinger <paul.holzinger@web.de>

1 files changed, 11 insertions, 11 deletions

diff --git a/docs/source/markdown/podman-manifest-add.1.md b/docs/source/markdown/podman-manifest-add.1.md
index f2d188766..c3c1ea1cf 100644
--- a/docs/source/markdown/podman-manifest-add.1.md
+++ b/docs/source/markdown/podman-manifest-add.1.md
@@ -15,25 +15,25 @@ The list image's ID.
 
 ## OPTIONS
 
-#### **--all**
+#### **\-\-all**
 
 If the image which should be added to the list or index is itself a list or
 index, add all of the contents to the local list.  By default, only one image
 from such a list or index will be added to the list or index.  Combining
 *--all* with any of the other options described below is NOT recommended.
 
-#### **--annotation** *annotation=value*
+#### **\-\-annotation** *annotation=value*
 
 Set an annotation on the entry for the newly-added image.
 
-#### **--arch**
+#### **\-\-arch**
 
 Override the architecture which the list or index records as a requirement for
 the image.  If *imageName* refers to a manifest list or image index, the
 architecture information will be retrieved from it.  Otherwise, it will be
 retrieved from the image's configuration information.
 
-#### **--authfile**=*path*
+#### **\-\-authfile**=*path*
 
 Path of the authentication file. Default is ${XDG\_RUNTIME\_DIR}/containers/auth.json, which is set using `podman login`.
 If the authorization state is not found there, $HOME/.docker/config.json is checked, which is set using `docker login`.
@@ -41,39 +41,39 @@ If the authorization state is not found there, $HOME/.docker/config.json is chec
 Note: You can also override the default path of the authentication file by setting the REGISTRY\_AUTH\_FILE
 environment variable. `export REGISTRY_AUTH_FILE=path`
 
-#### **--cert-dir**=*path*
+#### **\-\-cert-dir**=*path*
 
 Use certificates at *path* (\*.crt, \*.cert, \*.key) to connect to the registry.
 Default certificates directory is _/etc/containers/certs.d_. (This option is not available with the remote Podman client)
 
-#### **--creds**=*creds*
+#### **\-\-creds**=*creds*
 
 The [username[:password]] to use to authenticate with the registry if required.
 If one or both values are not supplied, a command line prompt will appear and the
 value can be entered.  The password is entered without echo.
 
-#### **--features**
+#### **\-\-features**
 
 Specify the features list which the list or index records as requirements for
 the image.  This option is rarely used.
 
-#### **--os**
+#### **\-\-os**
 
 Override the OS which the list or index records as a requirement for the image.
 If *imagename* refers to a manifest list or image index, the OS information
 will be retrieved from it.  Otherwise, it will be retrieved from the image's
 configuration information.
 
-#### **--os-version**
+#### **\-\-os-version**
 
 Specify the OS version which the list or index records as a requirement for the
 image.  This option is rarely used.
 
-#### **--tls-verify**
+#### **\-\-tls-verify**
 
 Require HTTPS and verify certificates when talking to container registries (defaults to true).
 
-#### **--variant**
+#### **\-\-variant**
 
 Specify the variant which the list or index records for the image.  This option
 is typically used to distinguish between multiple entries which share the same