docs/man: suggest using Git configuration for LFS keys

The documentation suggests using .lfsconfig in the repository root for
configuration keys.  Only a small number of keys can be set in this file
for security reasons, but we don't mention this until the end of the
file, which means that users often don't notice this fact, leading to
confusion when it doesn't work.

Instead, suggest primarily using the Git configuration files for storing
this data, since that will always work.  State that users can use
.lfsconfig, but tell them up front that it is restricted to a small
number of keys, and point them farther down the page where they can find
that information.  Indicate to users that this restriction is for
security reasons to help them better understand the rationale.

Author: bk2204

docs/man/git-lfs-config.5.ronn

@@ -3,12 +3,18 @@ git-lfs-config(5) -- Configuration options for git-lfs
 
 ## CONFIGURATION FILES
 
-git-lfs reads its configuration from a file called `.lfsconfig` at the root of
-the repository. The `.lfsconfig` file uses the same format as `.gitconfig`.
+git-lfs reads its configuration from any file supported by `git config -l`,
+including all per-repository, per-user, and per-system Git configuration files.
 
-Additionally, all settings can be overridden by values returned by `git config -l`.
-This allows you to override settings like `lfs.url` in your local environment
-without having to modify the `.lfsconfig` file.
+Additionally, a small number of settings can be specified in a file called
+`.lfsconfig` at the root of the repository; see the "LFSCONFIG" section for more
+details. This configuration file is useful for setting options such as the LFS
+URL or access type for all users of a repository, especially when these differ
+from the default. The `.lfsconfig` file uses the same format as `.gitconfig`.
+
+Settings from Git configuration files override the `.lfsconfig` file. This
+allows you to override settings like `lfs.url` in your local environment without
+having to modify the `.lfsconfig` file.
 
 Most options regarding git-lfs are contained in the `[lfs]` section, meaning
 they are all named `lfs.foo` or similar, although occasionally an lfs option can
@@ -350,6 +356,8 @@ including and limited to:
 - remote.{name}.lfsurl
 - remote.{name}.{*}.access
 
+The set of keys allowed in this file is restricted for security reasons.
+
 ## EXAMPLES
 
 *  Configure a custom LFS endpoint for your repository: