Merge 'nix flake {info,list-inputs}' into 'nix flake metadata'

Fixes #4613.

1 files changed, 110 insertions, 0 deletions

diff --git a/src/nix/flake-metadata.md b/src/nix/flake-metadata.md
new file mode 100644
index 000000000..5a009409b
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+++ b/src/nix/flake-metadata.md
@@ -0,0 +1,110 @@
+R""(
+
+# Examples
+
+* Show what `nixpkgs` resolves to:
+
+  ```console
+  # nix flake metadata nixpkgs
+  Resolved URL:  github:edolstra/dwarffs
+  Locked URL:    github:edolstra/dwarffs/f691e2c991e75edb22836f1dbe632c40324215c5
+  Description:   A filesystem that fetches DWARF debug info from the Internet on demand
+  Path:          /nix/store/769s05vjydmc2lcf6b02az28wsa9ixh1-source
+  Revision:      f691e2c991e75edb22836f1dbe632c40324215c5
+  Last modified: 2021-01-21 15:41:26
+  Inputs:
+  ├───nix: github:NixOS/nix/6254b1f5d298ff73127d7b0f0da48f142bdc753c
+  │   ├───lowdown-src: github:kristapsdz/lowdown/1705b4a26fbf065d9574dce47a94e8c7c79e052f
+  │   └───nixpkgs: github:NixOS/nixpkgs/ad0d20345219790533ebe06571f82ed6b034db31
+  └───nixpkgs follows input 'nix/nixpkgs'
+  ```
+
+* Show information about `dwarffs` in JSON format:
+
+  ```console
+  # nix flake metadata dwarffs --json | jq .
+  {
+    "description": "A filesystem that fetches DWARF debug info from the Internet on demand",
+    "lastModified": 1597153508,
+    "locked": {
+      "lastModified": 1597153508,
+      "narHash": "sha256-VHg3MYVgQ12LeRSU2PSoDeKlSPD8PYYEFxxwkVVDRd0=",
+      "owner": "edolstra",
+      "repo": "dwarffs",
+      "rev": "d181d714fd36eb06f4992a1997cd5601e26db8f5",
+      "type": "github"
+    },
+    "locks": { ... },
+    "original": {
+      "id": "dwarffs",
+      "type": "indirect"
+    },
+    "originalUrl": "flake:dwarffs",
+    "path": "/nix/store/hang3792qwdmm2n0d9nsrs5n6bsws6kv-source",
+    "resolved": {
+      "owner": "edolstra",
+      "repo": "dwarffs",
+      "type": "github"
+    },
+    "resolvedUrl": "github:edolstra/dwarffs",
+    "revision": "d181d714fd36eb06f4992a1997cd5601e26db8f5",
+    "url": "github:edolstra/dwarffs/d181d714fd36eb06f4992a1997cd5601e26db8f5"
+  }
+  ```
+
+# Description
+
+This command shows information about the flake specified by the flake
+reference *flake-url*. It resolves the flake reference using the
+[flake registry](./nix3-registry.md), fetches it, and prints some meta
+data. This includes:
+
+* `Resolved URL`: If *flake-url* is a flake identifier, then this is
+  the flake reference that specifies its actual location, looked up in
+  the flake registry.
+
+* `Locked URL`: A flake reference that contains a commit or content
+  hash and thus uniquely identifies a specific flake version.
+
+* `Description`: A one-line description of the flake, taken from the
+  `description` field in `flake.nix`.
+
+* `Path`: The store path containing the source code of the flake.
+
+* `Revision`: The Git or Mercurial commit hash of the locked flake.
+
+* `Revisions`: The number of ancestors of the Git or Mercurial commit
+  of the locked flake. Note that this is not available for `github`
+  flakes.
+
+* `Last modified`: For Git or Mercurial flakes, this is the commit
+  time of the commit of the locked flake; for tarball flakes, it's the
+  most recent timestamp of any file inside the tarball.
+
+* `Inputs`: The flake inputs with their corresponding lock file
+  entries.
+
+With `--json`, the output is a JSON object with the following fields:
+
+* `original` and `originalUrl`: The flake reference specified by the
+  user (*flake-url*) in attribute set and URL representation.
+
+* `resolved` and `resolvedUrl`: The resolved flake reference (see
+  above) in attribute set and URL representation.
+
+* `locked` and `lockedUrl`: The locked flake reference (see above) in
+  attribute set and URL representation.
+
+* `description`: See `Description` above.
+
+* `path`: See `Path` above.
+
+* `revision`: See `Revision` above.
+
+* `revCount`: See `Revisions` above.
+
+* `lastModified`: See `Last modified` above.
+
+* `locks`: The contents of `flake.lock`.
+
+)""