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-env/uninstall.md

@@ -0,0 +1,28 @@
+# Name
+
+`nix-env --uninstall` - remove packages from user environment
+
+# Synopsis
+
+`nix-env` {`--uninstall` | `-e`} *drvnames…*
+
+# Description
+
+The uninstall operation creates a new user environment, based on the
+current generation of the active profile, from which the store paths
+designated by the symbolic names *drvnames* are removed.
+
+{{#include ./opt-common.md}}
+
+{{#include ../opt-common.md}}
+
+{{#include ./env-common.md}}
+
+{{#include ../env-common.md}}
+
+# Examples
+
+```console
+$ nix-env --uninstall gcc
+$ nix-env --uninstall '.*' (remove everything)
+```