docs(notes): add Git garbage collection explanation

Author: lzwjava

_posts/en/2025-01-11-notes-en.md

@@ -7,7 +7,7 @@ generated: false
 translated: false
 ---
 
-These 2128 notes are primarily generated by AI chatbots. I used them to summarize key points and will walk through them to enhance my understanding.
+These 2129 notes are primarily generated by AI chatbots. I used them to summarize key points and will walk through them to enhance my understanding.
 
 * [AI Model Context Window Capacities](/notes/2025-09-03-ai-model-context-window-en)
 * [Alphabet Hits $186.66B in H1 2025](/notes/2025-09-03-alphabet-h1-2025-revenue-en)
@@ -18,6 +18,7 @@ These 2128 notes are primarily generated by AI chatbots. I used them to summariz
 * [Upgrade Claude Code Quickly Now](/notes/2025-09-03-claudecode-upgrade-quick-en)
 * [DBS H1 2025 Record Revenue Workforce Cuts](/notes/2025-09-03-dbs-h1-2025-revenue-cuts-en)
 * [Discipline Versus Speed Career Bets](/notes/2025-09-03-discipline-vs-speed-bets-en)
+* [Git Garbage Collection Explained](/notes/2025-09-03-git-garbage-collection-en)
 * [HSBC H1 2025 Revenue Drops but Grows Adjusted](/notes/2025-09-03-hsbc-h1-2025-revenue-en)
 * [Configuring JaCoCo Agent Output Directory](/notes/2025-09-03-jaccode-output-dir-en)
 * [JaCoCo Destfile Usage and Analysis](/notes/2025-09-03-jacoco-destfile-analysis-en)

notes/2025-09-03-git-garbage-collection-en.md

@@ -0,0 +1,40 @@
+---
+title: Git Garbage Collection Explained
+lang: en
+layout: post
+audio: false
+translated: false
+generated: true
+image: false
+---
+
+`git gc` stands for **Git garbage collection**. It’s a housekeeping command that cleans up and optimizes your local repository.
+
+### What it does
+
+* **Compresses file history**: Git stores objects (commits, trees, blobs) in a database. Over time, many loose objects accumulate. `git gc` packs them together into a compact binary file, saving disk space.
+* **Removes unreachable objects**: If you deleted branches or rebased, some commits may no longer be reachable from any reference. Git keeps them for safety, but `git gc` eventually cleans them up.
+* **Optimizes references**: It rewrites and packs refs like tags and branches to make lookups faster.
+* **Prunes reflogs**: Old reflog entries (records of HEAD changes) beyond the expiry period get removed.
+
+### Why it sometimes happens automatically
+
+* Git runs **automatic background `gc`** when the number of loose objects or pack files crosses a threshold. For example, if you’ve made a lot of commits, rebases, or merges, Git may trigger it.
+* Many Git commands (like `git fetch`, `git merge`, or `git rebase`) check whether a `gc` is advisable and run it automatically if needed.
+* This helps keep your repo performant without you having to think about it.
+
+### When to run it manually
+
+* If your repository feels **slow** or **bloated** (e.g., large `.git` folder).
+* After doing a **big cleanup** (like deleting branches or removing large files from history).
+* If you want to force immediate cleanup:
+
+  ```bash
+  git gc --prune=now --aggressive
+  ```
+
+  *(be careful: `--aggressive` can take a long time, especially on large repos)*
+
+---
+
+Do you want me to also explain how to **check when Git last ran `gc` automatically** and what thresholds trigger it?

original/2025-01-11-notes-en.md

@@ -7,7 +7,7 @@ generated: false
 translated: false
 ---
 
-These 2128 notes are primarily generated by AI chatbots. I used them to summarize key points and will walk through them to enhance my understanding.
+These 2129 notes are primarily generated by AI chatbots. I used them to summarize key points and will walk through them to enhance my understanding.
 
 * [AI Model Context Window Capacities](/notes/2025-09-03-ai-model-context-window-en)
 * [Alphabet Hits $186.66B in H1 2025](/notes/2025-09-03-alphabet-h1-2025-revenue-en)
@@ -18,6 +18,7 @@ These 2128 notes are primarily generated by AI chatbots. I used them to summariz
 * [Upgrade Claude Code Quickly Now](/notes/2025-09-03-claudecode-upgrade-quick-en)
 * [DBS H1 2025 Record Revenue Workforce Cuts](/notes/2025-09-03-dbs-h1-2025-revenue-cuts-en)
 * [Discipline Versus Speed Career Bets](/notes/2025-09-03-discipline-vs-speed-bets-en)
+* [Git Garbage Collection Explained](/notes/2025-09-03-git-garbage-collection-en)
 * [HSBC H1 2025 Revenue Drops but Grows Adjusted](/notes/2025-09-03-hsbc-h1-2025-revenue-en)
 * [Configuring JaCoCo Agent Output Directory](/notes/2025-09-03-jaccode-output-dir-en)
 * [JaCoCo Destfile Usage and Analysis](/notes/2025-09-03-jacoco-destfile-analysis-en)