Include cargo version in the generated manual

.github/workflows/deploy_docs.yml

@@ -13,6 +13,9 @@ jobs:
     steps:
       - uses: actions/checkout@v2
 
+      - name: Install jq
+        run: sudo apt-get install -y jq
+
       - uses: actions-rs/toolchain@v1
         with:
           profile: minimal

manual/book.toml

@@ -15,3 +15,6 @@ git-repository-url = "https://github.com/wilfred/difftastic"
 
 [output.html.playground]
 copyable = false
+
+[preprocessor.replace-version-placeholder]
+command = "./replace_version_placeholder.sh"

manual/replace_version_placeholder.sh

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+DFT_VERSION=$(cargo read-manifest | jq -r .version)
+
+jq .[1] | jq '.sections[0].Chapter.content |= sub("DFT_VERSION_HERE"; "'$DFT_VERSION'")'

manual/src/introduction.md

@@ -6,7 +6,7 @@ Difftastic is a diff tool that understands syntax. It supports [over
 Difftastic is open source software (MIT license) and [available on
 GitHub](https://github.com/wilfred/difftastic).
 
-This manual tracks the bleeding edge version of difftastic. The
+This copy of the manual describes version DFT_VERSION_HERE. The
 [changelog](https://github.com/Wilfred/difftastic/blob/master/CHANGELOG.md)
 records which features and bug fixes are in each version.