From 42cc98f8d66627ff7e396fb809034d3389b3bd0a Mon Sep 17 00:00:00 2001
From: Eelco Dolstra <edolstra@gmail.com>
Date: Tue, 8 Dec 2020 21:52:22 +0100
Subject: [PATCH] Add 'nix develop' and `nix print-dev-env' manpages

---
 src/nix/develop.cc       | 38 ++++------------
 src/nix/develop.md       | 94 ++++++++++++++++++++++++++++++++++++++++
 src/nix/print-dev-env.md | 19 ++++++++
 3 files changed, 121 insertions(+), 30 deletions(-)
 create mode 100644 src/nix/develop.md
 create mode 100644 src/nix/print-dev-env.md

diff --git a/src/nix/develop.cc b/src/nix/develop.cc
index 457d94382..edd87f246 100644
--- a/src/nix/develop.cc
+++ b/src/nix/develop.cc
@@ -385,30 +385,11 @@ struct CmdDevelop : Common, MixEnvironment
         return "run a bash shell that provides the build environment of a derivation";
     }
 
-    Examples examples() override
+    std::string doc() override
     {
-        return {
-            Example{
-                "To get the build environment of GNU hello:",
-                "nix develop nixpkgs#hello"
-            },
-            Example{
-                "To get the build environment of the default package of flake in the current directory:",
-                "nix develop"
-            },
-            Example{
-                "To store the build environment in a profile:",
-                "nix develop --profile /tmp/my-shell nixpkgs#hello"
-            },
-            Example{
-                "To use a build environment previously recorded in a profile:",
-                "nix develop /tmp/my-shell"
-            },
-            Example{
-                "To replace all occurences of a store path with a writable directory:",
-                "nix develop --redirect nixpkgs#glibc.dev ~/my-glibc/outputs/dev"
-            },
-        };
+        return
+          #include "develop.md"
+          ;
     }
 
     void run(ref<Store> store) override
@@ -495,14 +476,11 @@ struct CmdPrintDevEnv : Common
         return "print shell code that can be sourced by bash to reproduce the build environment of a derivation";
     }
 
-    Examples examples() override
+    std::string doc() override
     {
-        return {
-            Example{
-                "To apply the build environment of GNU hello to the current shell:",
-                ". <(nix print-dev-env nixpkgs#hello)"
-            },
-        };
+        return
+          #include "print-dev-env.md"
+          ;
     }
 
     Category category() override { return catUtility; }
diff --git a/src/nix/develop.md b/src/nix/develop.md
new file mode 100644
index 000000000..7a906d10d
--- /dev/null
+++ b/src/nix/develop.md
@@ -0,0 +1,94 @@
+R""(
+
+# Examples
+
+* Start a shell with the build environment of the default package of
+  the flake in the current directory:
+
+  ```console
+  # nix develop
+  ```
+
+  Typical commands to run inside this shell are:
+
+  ```console
+  # configurePhase
+  # buildPhase
+  # installPhase
+  ```
+
+  Alternatively, you can run whatever build tools your project uses
+  directly, e.g. for a typical Unix project:
+
+  ```console
+  # ./configure --prefix=$out
+  # make
+  # make install
+  ```
+
+* Run a particular build phase directly:
+
+  ```console
+  # nix develop --configure
+  # nix develop --build
+  # nix develop --check
+  # nix develop --install
+  # nix develop --installcheck
+  ```
+
+* Start a shell with the build environment of GNU Hello:
+
+  ```console
+  # nix develop nixpkgs#hello
+  ```
+
+* Record a build environment in a profile:
+
+  ```console
+  # nix develop --profile /tmp/my-build-env nixpkgs#hello
+  ```
+
+* Use a build environment previously recorded in a profile:
+
+  ```cosnole
+  # nix develop /tmp/my-build-env
+  ```
+
+* Replace all occurences of the store path corresponding to
+  `glibc.dev` with a writable directory:
+
+  ```console
+  # nix develop --redirect nixpkgs#glibc.dev ~/my-glibc/outputs/dev
+  ```
+
+  Note that this is useful if you're running a `nix develop` shell for
+  `nixpkgs#glibc` in `~/my-glibc` and want to compile another package
+  against it.
+
+# Description
+
+`nix develop` starts a `bash` shell that provides an interactive build
+environment nearly identical to what Nix would use to build
+*installable*. Inside this shell, environment variables and shell
+functions are set up so that you can interactively and incrementally
+build your package.
+
+Nix determines the build environment by building a modified version of
+the derivation *installable* that just records the environment
+initialised by `stdenv` and exits. This build environment can be
+recorded into a profile using `--profile`.
+
+The prompt used by the `bash` shell can be customised by setting the
+`bash-prompt` and `bash-prompt-suffix` settings in `nix.conf` or in
+the flake's `nixConfig` attribute.
+
+# Flake output attributes
+
+If no flake output attribute is given, `nix run` tries the following
+flake output attributes:
+
+* `devShell.<system>`
+
+* `defaultPackage.<system>`
+
+)""
diff --git a/src/nix/print-dev-env.md b/src/nix/print-dev-env.md
new file mode 100644
index 000000000..b80252acf
--- /dev/null
+++ b/src/nix/print-dev-env.md
@@ -0,0 +1,19 @@
+R""(
+
+# Examples
+
+* Apply the build environment of GNU hello to the current shell:
+
+  ```console
+  # . <(nix print-dev-env nixpkgs#hello)
+  ```
+
+# Description
+
+This command prints a shell script that can be sourced by `b`ash and
+that sets the environment variables and shell functions defined by the
+build process of *installable*. This allows you to get a similar build
+environment in your current shell rather than in a subshell (as with
+`nix develop`).
+
+)""