feat: add prefix command

mkdocs/prefix.md

@@ -0,0 +1,96 @@
+Paths can be prefixed using the 'prefix' command.
+The complete yaml content will be nested inside the new prefix path.
+
+```
+yq p <yaml_file> <path>
+```
+
+### To Stdout
+Given a data1.yaml file of:
+```yaml
+a: simple
+b: [1, 2]
+```
+then
+```bash
+yq p data1.yaml c
+```
+will output:
+```yaml
+c:
+  a: simple
+  b: [1, 2]
+```
+
+### Arbitrary depth
+Given a data1.yaml file of:
+```yaml
+a:
+  b: [1, 2]
+```
+then
+```bash
+yq p data1.yaml c.d
+```
+will output:
+```yaml
+c:
+  d:
+    a:
+      b: [1, 2]
+```
+
+### Updating files in-place
+Given a data1.yaml file of:
+```yaml
+a: simple
+b: [1, 2]
+```
+then
+```bash
+yq p -i data1.yaml c
+```
+will update the data1.yaml file so that the path 'c' is prefixed to all other paths.
+
+### Multiple Documents - update a single document
+Given a data1.yaml file of:
+```yaml
+something: else
+---
+a: simple
+b: cat
+```
+then
+```bash
+yq p -d1 data1.yaml c
+```
+will output:
+```yaml
+something: else
+---
+c:
+  a: simple
+  b: cat
+```
+
+### Multiple Documents - update a single document
+Given a data1.yaml file of:
+```yaml
+something: else
+---
+a: simple
+b: cat
+```
+then
+```bash
+yq p -d'*' data1.yaml c
+```
+will output:
+```yaml
+c:
+  something: else
+---
+c:
+  a: simple
+  b: cat
+```