Show preview of entire command in history search (#125)

Long commands get truncated in the fzf finder, while the spacing of multi-line commands are messed up. To remedy this, show a preview of the entire command at the bottom.

Author: ovv

README.md

@@ -47,6 +47,7 @@ Use `fzf.fish` to interactively find and insert into the command line:
 
 - **Search input:** the command history from all interactive sessions of Fish
 - **Key binding and mnemonic:** <kbd>Ctrl</kbd>+<kbd>R</kbd> (`R` for reverse-i-search)
+- **Preview window:** the entire command, wrapped
 
 ### A shell variable
 

functions/__fzf_search_history.fish

@@ -4,7 +4,10 @@ function __fzf_search_history --description "Search command history. Replace the
     set command_with_ts (
         # Reference https://devhints.io/strftime to understand strftime format symbols
         builtin history --null --show-time="%m-%d %H:%M:%S | " |
-        fzf --read0 --tiebreak=index --query=(commandline) |
+        fzf --read0 --tiebreak=index --query=(commandline) \
+            # preview current command in a window at the bottom 3 lines tall
+            --preview="echo {4..}" \
+            --preview-window="bottom:3:wrap" |
         string collect
     )