Rename doc/manual{src -> source}

This is needed to avoid this
https://github.com/mesonbuild/meson/issues/13774 when we go back to
making our subproject directory `src`.

doc/manual/source/command-ref/nix-copy-closure.md

@@ -0,0 +1,91 @@
+# Name
+
+`nix-copy-closure` - copy store objects to or from a remote machine via SSH
+
+# Synopsis
+
+`nix-copy-closure`
+  [`--to` | `--from` ]
+  [`--gzip`]
+  [`--include-outputs`]
+  [`--use-substitutes` | `-s`]
+  [`-v`]
+  [_user_@]_machine_[:_port_] _paths_
+
+# Description
+
+Given _paths_ from one machine, `nix-copy-closure` computes the [closure](@docroot@/glossary.md#gloss-closure) of those paths (i.e. all their dependencies in the Nix store), and copies [store objects](@docroot@/glossary.md#gloss-store-object) in that closure to another machine via SSH.
+It doesn’t copy store objects that are already present on the other machine.
+
+> **Note**
+>
+> While the Nix store to use on the local machine can be specified on the command line with the [`--store`](@docroot@/command-ref/conf-file.md#conf-store) option, the Nix store to be accessed on the remote machine can only be [configured statically](@docroot@/command-ref/conf-file.md#configuration-file) on that remote machine.
+
+Since `nix-copy-closure` calls `ssh`, you may need to authenticate with the remote machine.
+In fact, you may be asked for authentication _twice_ because `nix-copy-closure` currently connects twice to the remote machine: first to get the set of paths missing on the target machine, and second to send the dump of those paths.
+When using public key authentication, you can avoid typing the passphrase with `ssh-agent`.
+
+# Options
+
+- `--to`
+
+  Copy the closure of _paths_ from a Nix store accessible from the local machine to the Nix store on the remote _machine_.
+  This is the default behavior.
+
+- `--from`
+
+  Copy the closure of _paths_ from the Nix store on the remote _machine_ to the local machine's specified Nix store.
+
+- `--gzip`
+
+  Enable compression of the SSH connection.
+
+- `--include-outputs`
+
+  Also copy the outputs of [store derivation]s included in the closure.
+
+  [store derivation]: @docroot@/glossary.md#gloss-store-derivation
+
+- `--use-substitutes` / `-s`
+
+  Attempt to download missing store objects on the target from [substituters](@docroot@/command-ref/conf-file.md#conf-substituters).
+  Any store objects that cannot be substituted on the target are still copied normally from the source.
+  This is useful, for instance, if the connection between the source and target machine is slow, but the connection between the target machine and `cache.nixos.org` (the default binary cache server) is fast.
+
+{{#include ./opt-common.md}}
+
+# Environment variables
+
+- `NIX_SSHOPTS`
+
+  Additional options to be passed to `ssh` on the command line.
+
+{{#include ./env-common.md}}
+
+# Examples
+
+> **Example**
+>
+> Copy GNU Hello with all its dependencies to a remote machine:
+>
+> ```shell-session
+> $ storePath="$(nix-build '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello --no-out-link)"
+> $ nix-copy-closure --to alice@itchy.example.org "$storePath"
+> copying 5 paths...
+> copying path '/nix/store/nrwkk6ak3rgkrxbqhsscb01jpzmslf2r-xgcc-13.2.0-libgcc' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/gm61h1y42pqyl6178g90x8zm22n6pyy5-libunistring-1.1' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/ddfzjdykw67s20c35i7a6624by3iz5jv-libidn2-2.3.7' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/apab5i73dqa09wx0q27b6fbhd1r18ihl-glibc-2.39-31' to 'ssh://alice@itchy.example.org'...
+> copying path '/nix/store/g1n2vryg06amvcc1avb2mcq36faly0mh-hello-2.12.1' to 'ssh://alice@itchy.example.org'...
+> ```
+
+> **Example**
+>
+> Copy GNU Hello from a remote machine using a known store path, and run it:
+>
+> ```shell-session
+> $ storePath="$(nix-instantiate --eval '<nixpkgs>' -I nixpkgs=channel:nixpkgs-unstable -A hello.outPath | tr -d '"')"
+> $ nix-copy-closure --from alice@itchy.example.org "$storePath"
+> $ "$storePath"/bin/hello
+> Hello, world!
+> ```