Add more options for shell commands

This commit introduces an extended configuration syntax for shell
commands. This syntax allows for specifying whether the stdin, stdout,
and stderr streams are enabled.

1 files changed, 27 insertions, 4 deletions

diff --git a/README.md b/README.md
index 5b77cf0..bc20e9d 100644
--- a/README.md
+++ b/README.md
@@ -159,15 +159,28 @@ base directory (that is specified when running the installer).
 
 #### Format
 
-Shell commands are specified as an array of commands, where each command is a
-two element array containing the actual shell command as the first element and
-a human-readable description as the second element.
+Shell commands can be specified in several different ways. The simplest way is
+just to specify a command as a string containing the command to be run. Another
+way is to specify a two element array where the first element is the shell
+command and the second is an optional human-readable description. Shell
+commands support an extended syntax as well, which provides more fine-grained
+control. A command can be specified as a dictionary that contains the command
+to be run, a description, and whether stdin, stdout, and stderr are enabled. In
+this syntax, all keys are optional except for the command itself.
 
 ##### Example (YAML)
 
 ```yaml
 - shell:
+  - mkdir -p ~/src
   - [mkdir -p ~/downloads, Creating downloads directory]
+  -
+    command: read var && echo Your variable is $var
+    stdin: true
+    stdout: true
+  -
+    command: read fail
+    stderr: true
 ```
 
 ##### Example (JSON)
@@ -175,7 +188,17 @@ a human-readable description as the second element.
 ```json
 [{
     "shell": [
-        ["mkdir -p ~/downloads", "Creating downloads directory"]
+        "mkdir -p ~/src",
+        ["mkdir -p ~/downloads", "Creating downloads directory"],
+        {
+            "command": "read var && echo Your variable is $var",
+            "stdin": true,
+            "stdout": true
+        },
+        {
+            "command": "read fail",
+            "stderr": true
+        }
     ]
 }]
 ```