feat: add 6 new playbook recipe pages

Add recipes for subtrees, hooks, remote management, diffing, history,
and selectors — covering all Git commands taught in the tutorial that
were missing from the playbook.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: braboj

chapters/playbook/diffing.md

@@ -0,0 +1,67 @@
+---
+title: "Diffing"
+description: "Git recipes for comparing unstaged changes, staged changes, branches, commits, and specific files."
+section: "playbook/diffing"
+order: 85
+---
+
+## Diffing
+
+### Show unstaged changes
+
+```text
+$ git diff
+```
+
+Compares working tree against the index (staged snapshot).
+
+### Show staged changes
+
+```text
+$ git diff --staged
+```
+
+Compares the index against the last commit — shows what will go into
+the next commit.
+
+### Compare two branches
+
+```text
+$ git diff main feature/name
+```
+
+Shows all differences between the tips of both branches.
+
+### Compare two commits
+
+```text
+$ git diff abc1234 def5678
+```
+
+### Show changes introduced by a single commit
+
+```text
+$ git diff HEAD~1 HEAD
+```
+
+Or use `git show` for the same result with commit metadata:
+
+```text
+$ git show HEAD
+```
+
+### Diff a specific file
+
+```text
+$ git diff -- path/to/file
+$ git diff --staged -- path/to/file
+```
+
+### Diff with statistics only
+
+```text
+$ git diff --stat main feature/name
+```
+
+Shows a summary of changed files and line counts without the full
+patch.

chapters/playbook/history.md

@@ -0,0 +1,69 @@
+---
+title: "History"
+description: "Git recipes for viewing, formatting, and filtering commit history — log output, author filters, date ranges, and path-based searches."
+section: "playbook/history"
+order: 86
+---
+
+## History
+
+### Compact one-line log
+
+```text
+$ git log --oneline
+```
+
+### Graph view with branches
+
+```text
+$ git log --oneline --graph --all
+```
+
+Shows the full branch topology in ASCII art.
+
+### Filter by author
+
+```text
+$ git log --author="Branko" --oneline
+```
+
+Matches against the author name or email. Supports regex.
+
+### Filter by date range
+
+```text
+$ git log --after="2025-01-01" --before="2025-06-30" --oneline
+```
+
+### Filter by file path
+
+```text
+$ git log -- path/to/file --oneline
+```
+
+Shows only commits that modified the specified file.
+
+### Custom format
+
+```text
+$ git log --format="%h %an %s" -10
+```
+
+Common placeholders: `%h` (short hash), `%an` (author name),
+`%s` (subject), `%ar` (relative date), `%d` (refs).
+
+### Show changes in each commit
+
+```text
+$ git log -p -3
+```
+
+Combines log output with the full diff for the last 3 commits.
+
+### Count commits per author
+
+```text
+$ git shortlog -sn
+```
+
+Useful for understanding contribution distribution.

chapters/playbook/hooks.md

@@ -0,0 +1,65 @@
+---
+title: "Hooks"
+description: "Git recipes for creating pre-commit and commit-msg hooks, sharing hooks across a team, and bypassing hooks when needed."
+section: "playbook/hooks"
+order: 83
+---
+
+## Hooks
+
+### Create a pre-commit hook
+
+```text
+$ cat > .git/hooks/pre-commit << 'EOF'
+#!/bin/sh
+# Reject commits that contain TODO
+if git diff --cached --quiet -S "TODO"; then
+  exit 0
+fi
+echo "Error: commit contains TODO"
+exit 1
+EOF
+$ chmod +x .git/hooks/pre-commit
+```
+
+The hook runs before every commit. A non-zero exit code aborts the
+commit.
+
+### Create a commit-msg hook
+
+```text
+$ cat > .git/hooks/commit-msg << 'EOF'
+#!/bin/sh
+# Enforce minimum message length
+if [ $(wc -c < "$1") -lt 10 ]; then
+  echo "Error: commit message too short"
+  exit 1
+fi
+EOF
+$ chmod +x .git/hooks/commit-msg
+```
+
+Receives the commit message file as `$1`. Useful for enforcing
+message conventions.
+
+### Share hooks with the team
+
+```text
+$ mkdir .githooks
+$ cp .git/hooks/pre-commit .githooks/
+$ git config core.hooksPath .githooks
+$ git add .githooks/
+$ git commit -m "Add shared hooks"
+```
+
+Everyone who clones the repo runs `git config core.hooksPath .githooks`
+to activate the shared hooks.
+
+### Bypass a hook
+
+```text
+$ git commit --no-verify -m "WIP: skip hooks"
+$ git push --no-verify
+```
+
+Use sparingly — hooks exist for a reason.

chapters/playbook/index.md

@@ -29,3 +29,9 @@ see [Glossary](../09-glossary.md).
 | [Submodules](submodules.md) | Add, clone, update, and remove submodules |
 | [Debugging](debugging.md) | Bisect, blame, and search commit history |
 | [Configuration](configuration.md) | Identity, defaults, aliases, and diagnostics |
+| [Subtrees](subtrees.md) | Add, pull, push, and remove subtrees |
+| [Hooks](hooks.md) | Pre-commit, commit-msg, sharing hooks, bypassing |
+| [Remote Management](remote-management.md) | Add, rename, remove remotes, switch URL, SSH setup |
+| [Diffing](diffing.md) | Unstaged, staged, between branches, commits, and files |
+| [History](history.md) | Log formatting, filtering by author, date, and path |
+| [Selectors](selectors.md) | Tilde, caret, double-dot, triple-dot, reflog refs |

chapters/playbook/remote-management.md

@@ -0,0 +1,57 @@
+---
+title: "Remote Management"
+description: "Git recipes for adding, renaming, and removing remotes, switching remote URLs, and setting up SSH authentication."
+section: "playbook/remote-management"
+order: 84
+---
+
+## Remote Management
+
+### List remotes
+
+```text
+$ git remote -v
+```
+
+Shows all configured remotes with their fetch and push URLs.
+
+### Add a remote
+
+```text
+$ git remote add upstream <url>
+```
+
+Common when working with forks — `origin` is your fork, `upstream`
+is the original repository.
+
+### Rename a remote
+
+```text
+$ git remote rename origin old-origin
+```
+
+### Remove a remote
+
+```text
+$ git remote remove upstream
+```
+
+Also removes all remote-tracking branches for that remote.
+
+### Switch a remote URL (HTTPS to SSH)
+
+```text
+$ git remote set-url origin git@github.com:<user>/<repo>.git
+```
+
+### Set up SSH authentication
+
+```text
+$ ssh-keygen -t ed25519 -C "you@example.com"
+$ eval "$(ssh-agent -s)"
+$ ssh-add ~/.ssh/id_ed25519
+$ ssh -T git@github.com                    # verify connection
+```
+
+Add the public key (`~/.ssh/id_ed25519.pub`) to your GitHub account
+under Settings > SSH Keys.

chapters/playbook/selectors.md

@@ -0,0 +1,63 @@
+---
+title: "Selectors"
+description: "Git recipes for navigating history with tilde, caret, double-dot, triple-dot, and reflog selectors."
+section: "playbook/selectors"
+order: 87
+---
+
+## Selectors
+
+### Navigate to a parent commit (tilde)
+
+```text
+$ git show HEAD~1                   # parent
+$ git show HEAD~3                   # great-grandparent
+```
+
+Tilde follows the first-parent chain. `HEAD~3` means "go back 3
+commits along the first parent."
+
+### Select a specific parent (caret)
+
+```text
+$ git show HEAD^1                   # first parent
+$ git show HEAD^2                   # second parent (merge commits)
+```
+
+Caret selects which parent of a merge commit to follow. Only
+meaningful on merge commits — `^1` and `^2` differ.
+
+### Combine tilde and caret
+
+```text
+$ git show HEAD~1^2                 # second parent of the previous commit
+```
+
+### Commits on one branch but not another (double-dot)
+
+```text
+$ git log main..feature --oneline
+```
+
+Shows commits reachable from `feature` that are not reachable from
+`main` — what would be merged.
+
+### Symmetric difference (triple-dot)
+
+```text
+$ git log --left-right main...feature --oneline
+```
+
+Shows commits on either branch but not both. The `--left-right`
+flag marks each commit with `<` (left) or `>` (right).
+
+### Reflog selectors
+
+```text
+$ git show HEAD@{1}                 # previous position of HEAD
+$ git show main@{yesterday}         # where main was yesterday
+$ git show HEAD@{2.hours.ago}       # HEAD two hours ago
+```
+
+Reflog entries expire after 90 days (reachable) or 30 days
+(unreachable) by default.

chapters/playbook/subtrees.md

@@ -0,0 +1,44 @@
+---
+title: "Subtrees"
+description: "Git recipes for adding, pulling, pushing, and removing subtrees — embedding external repositories without submodules."
+section: "playbook/subtrees"
+order: 82
+---
+
+## Subtrees
+
+### Add a subtree
+
+```text
+$ git subtree add --prefix=libs/utils <url> main --squash
+$ git commit -m "Add utils subtree"
+```
+
+The `--squash` flag merges all upstream history into a single commit.
+
+### Pull updates from the upstream repository
+
+```text
+$ git subtree pull --prefix=libs/utils <url> main --squash
+```
+
+Fetches upstream changes and merges them into the subtree directory.
+
+### Push changes back to the upstream repository
+
+```text
+$ git subtree push --prefix=libs/utils <url> main
+```
+
+Extracts commits that touch the subtree directory and pushes them
+upstream.
+
+### Remove a subtree
+
+```text
+$ git rm -r libs/utils
+$ git commit -m "Remove utils subtree"
+```
+
+Unlike submodules, there is no metadata to clean up — just remove
+the directory.