Add {{#shiftinclude}} command

guide/src/format/mdbook.md

@@ -211,6 +211,25 @@ This is the full file.
 
 Lines containing anchor patterns inside the included anchor are ignored.
 
+## Including a file but changing its indentation
+
+Sometimes it is useful to include a file or part of a file but with the indentation shifted,
+using the following syntax:
+
+```hbs
+\{{#shiftinclude -2:file.rs}}
+```
+
+A positive number for the shift will prepend spaces to all lines; a negative number will remove
+the corresponding number of whitespace characters from the beginning of each line (leaving
+intact any non-whitespace).
+
+The special `auto` value will remove common initial whitespace from all lines.
+
+```hbs
+\{{#shiftinclude auto:file.rs:indentedanchor}}
+```
+
 ## Including a file but initially hiding all except specified lines
 
 The `rustdoc_include` helper is for including code from external Rust files that contain complete

src/utils/mod.rs

@@ -15,8 +15,8 @@ use std::fmt::Write;
 use std::path::Path;
 
 pub use self::string::{
-    take_anchored_lines, take_lines, take_rustdoc_include_anchored_lines,
-    take_rustdoc_include_lines,
+    take_anchored_lines, take_anchored_lines_with_shift, take_lines, take_lines_with_shift,
+    take_rustdoc_include_anchored_lines, take_rustdoc_include_lines, Shift,
 };
 
 /// Replaces multiple consecutive whitespace characters with a single space character.

tests/dummy_book/src/first/nested-test-with-anchors.rs

@@ -9,3 +9,11 @@ assert!(!$TEST_STATUS);
 // unique-string-for-anchor-test
 assert!($TEST_STATUS);
 // ANCHOR_END: myanchor
+
+pub mod indent {
+    // ANCHOR: indentedanchor
+    pub fn indented_function() {
+        // This extra indent remains
+    }
+    // ANCHOR_END: indentedanchor
+}

tests/dummy_book/src/first/nested.md

@@ -18,6 +18,16 @@ assert!($TEST_STATUS);
 {{#include nested-test-with-anchors.rs:myanchor}}
 ```
 
+## Includes can be shifted
+
+```rust
+{{#shiftinclude +2:nested-test-with-anchors.rs:myanchor}}
+```
+
+```rust
+{{#shiftinclude auto:nested-test-with-anchors.rs:indentedanchor}}
+```
+
 ## Rustdoc include adds the rest of the file as hidden
 
 ```rust