Update docs.

README.mkd

@@ -297,7 +297,7 @@ By default the sign column will appear when there are signs to show and disappea
 set signcolumn=yes
 ```
 
-GitGutter can preserve or ignore non-gitgutter signs.  On Vim and Neovim < 0.4.0, gitgutter will default to preserving other signs; on Neovim >= 0.4.0 gitgutter defaults to ignoring them.  You can control this with:
+GitGutter can preserve or ignore non-gitgutter signs.  For Vim v8.1.0614 and later you can set gitgutter's signs' priorities with `g:gitgutter_sign_priority`, so gitgutter defaults to clobbering other signs.  For Neovim v0.4.0 and later you can set an expanding sign column so gitgutter again defaults to clobbering other signs.  Otherwise, gitgutter defaults to preserving other signs.  You can configure this with:
 
 ```viml
 let g:gitgutter_sign_allow_clobber = 1

doc/gitgutter.txt

@@ -287,6 +287,8 @@ Signs:~
     |g:gitgutter_highlight_lines|
     |g:gitgutter_highlight_linenrs|
     |g:gitgutter_max_signs|
+    |g:gitgutter_sign_priority|
+    |g:gitgutter_sign_allow_clobber|
     |g:gitgutter_sign_added|
     |g:gitgutter_sign_modified|
     |g:gitgutter_sign_removed|
@@ -385,9 +387,14 @@ signs, so to avoid slowing down the GUI the number of signs is capped.  When
 the number of changed lines exceeds this value, the plugin removes all signs
 and displays a warning message.
 
+                                                   *g:gitgutter_sign_priority*
+Default: 10
+
+Sets the |sign-priority| gitgutter assigns to its signs.
+
                                                *g:gitgutter_sign_allow_clobber*
-Default: 0 (Vim, Neovim < 0.4.0)
+Default: 0 (Vim < 8.1.0614, Neovim < 0.4.0)
-         1 (Neovim >= 0.4.0)
+         1 (otherwise)
 
 Determines whether gitgutter preserves non-gitgutter signs. When 1, gitgutter
 will not preserve non-gitgutter signs.