nix flake update: Recreate the lock file

This is probably what most people expect it to do. Fixes #3781.

There is a new command 'nix flake lock' that has the old behaviour of
'nix flake update', i.e. it just adds missing lock file entries unless
overriden using --update-input.

1 files changed, 9 insertions, 28 deletions

diff --git a/src/nix/flake-update.md b/src/nix/flake-update.md
index a2ffedd2a..03b50e38e 100644
--- a/src/nix/flake-update.md
+++ b/src/nix/flake-update.md
@@ -2,52 +2,33 @@ R""(
 
 # Examples
 
-* Update the `nixpkgs` and `nix` inputs of the flake in the current
-  directory:
-
-  ```console
-  # nix flake update --update-input nixpkgs --update-input nix
-  * Updated 'nix': 'github:NixOS/nix/9fab14adbc3810d5cc1f88672fde1eee4358405c' -> 'github:NixOS/nix/8927cba62f5afb33b01016d5c4f7f8b7d0adde3c'
-  * Updated 'nixpkgs': 'github:NixOS/nixpkgs/3d2d8f281a27d466fa54b469b5993f7dde198375' -> 'github:NixOS/nixpkgs/a3a3dda3bacf61e8a39258a0ed9c924eeca8e293'
-  ```
-
 * Recreate the lock file (i.e. update all inputs) and commit the new
   lock file:
 
   ```console
-  # nix flake update --recreate-lock-file --commit-lock-file
+  # nix flake update
+  * Updated 'nix': 'github:NixOS/nix/9fab14adbc3810d5cc1f88672fde1eee4358405c' -> 'github:NixOS/nix/8927cba62f5afb33b01016d5c4f7f8b7d0adde3c'
+  * Updated 'nixpkgs': 'github:NixOS/nixpkgs/3d2d8f281a27d466fa54b469b5993f7dde198375' -> 'github:NixOS/nixpkgs/a3a3dda3bacf61e8a39258a0ed9c924eeca8e293'
   …
   warning: committed new revision '158bcbd9d6cc08ab859c0810186c1beebc982aad'
   ```
 
 # Description
 
-This command updates the lock file of a flake (`flake.lock`) so that
-it contains a lock for every flake input specified in
-`flake.nix`. Note that every command that operates on a flake will
-also update the lock file if needed, and supports the same
-flags. Therefore,
+This command recreates the lock file of a flake (`flake.lock`), thus
+updating the lock for every mutable input (like `nixpkgs`) to its
+current version. This is equivalent to passing `--recreate-lock-file`
+to any command that operates on a flake. That is,
 
 ```console
-# nix flake update --update-input nixpkgs
+# nix flake update
 # nix build
 ```
 
 is equivalent to:
 
 ```console
-# nix build --update-input nixpkgs
+# nix build --recreate-lock-file
 ```
 
-Thus, this command is only useful if you want to update the lock file
-separately from any other action such as building.
-
-> **Note**
->
-> This command does *not* update locks that are already present unless
-> you explicitly ask for it using `--update-input` or
-> `--recreate-lock-file`. Thus, if the lock file already has locks for
-> every input, then `nix flake update` (without arguments) does
-> nothing.
-
 )""