Add $FZF_DEFAULT_OPTS_FILE (#3618)

For those who prefer to manage default options in a file.
If the file is not found, fzf will exit with an error.

We're not setting a default value for it because:

1. it's hard to find a default value that can be universally agreed upon
2. to avoid fzf having to check for the existence of the file even when it's not used

1 files changed, 4 insertions, 0 deletions

diff --git a/README.md b/README.md
index 4c9b01fd..e0b367b6 100644
--- a/README.md
+++ b/README.md
@@ -329,6 +329,10 @@ or `py`.
 - `FZF_DEFAULT_OPTS`
     - Default options
     - e.g. `export FZF_DEFAULT_OPTS="--layout=reverse --inline-info"`
+- `FZF_DEFAULT_OPTS_FILE`
+    - If you prefer to manage default options in a file, set this variable to
+      point to the location of the file
+    - e.g. `export FZF_DEFAULT_OPTS_FILE=~/.fzfrc`
 
 ### Options