[Search git status] preview changed files (#237)

Show a preview of the unstaged and staged changes of the hovered-over file. This will make it easier to identify which files to select and perhaps offer a faster-to-navigate alternative to git diff.

README.md

@@ -32,6 +32,7 @@ Use `fzf.fish` to interactively find and insert the shell entities listed below
 
 - **Search input:** the current repository's `git status`
 - **Key binding and mnemonic:** <kbd>Ctrl</kbd>+<kbd>Alt</kbd>+<kbd>S</kbd> (`S` for status)
+- **Preview window:** the unstaged and staged changes in the file
 
 ### Commit hashes
 

functions/_fzf_preview_changed_file.fish

@@ -0,0 +1,19 @@
+# helper for _fzf_search_git_status
+# arg should be a line from git status --short, something like...
+# MM functions/_fzf_preview_changed_file.fish
+function _fzf_preview_changed_file
+    set -l path (string split ' ' $argv)[-1]
+    if string match -r '^\?\?' $argv --quiet
+        echo -e (set_color --underline)=== Untracked ===\n
+        _fzf_preview_file $path
+    else
+        if string match -r '\S\s\S' $argv --quiet
+            echo -e (set_color --underline red)=== Unstaged ===\n
+            git diff --color=always -- $path
+        end
+        if string match -r '^\S' $argv --quiet
+            echo -e (set_color --underline green)=== Staged ===\n
+            git diff --color=always --staged -- $path
+        end
+    end
+end

functions/_fzf_preview_file.fish

@@ -1,4 +1,4 @@
-# helper function for _fzf_search_directory
+# helper function for _fzf_search_directory and _fzf_search_git_status
 function _fzf_preview_file --description "Print a preview for the given file based on its file type."
     # because there's no way to guarantee that _fzf_search_directory passes the path to _fzf_preview_file
     # as one argument, we collect all the arguments into one single variable and treat that as the path

functions/_fzf_search_git_status.fish

@@ -8,6 +8,7 @@ function _fzf_search_git_status --description "Search the output of git status.
             _fzf_wrapper --ansi \
                 --multi \
                 --query=(commandline --current-token) \
+                --preview='_fzf_preview_changed_file {}' \
                 $fzf_git_status_opts
         )
         if test $status -eq 0