docs: Clarify that tag fetch defaults did not change in v6

Section 3 incorrectly claimed that FetchOptions defaulted to AllTags in v5
and changed to NoTags in v6. This was false.

Actual behavior (both v5 and v6):
- CloneOptions.Tags defaults to AllTags
- FetchOptions.Tags defaults to TagFollowing (not AllTags, not NoTags)

TagFollowing fetches tags reachable from fetched commits, matching git CLI
behavior. This has been the default in both v5 and v6.

PR #1459 was not a behavior change - it only fixed a test that incorrectly
expected AllTags behavior without setting it explicitly.

Changes made:
- Corrected section 3 to clarify no default behavior changed
- Explained what TagFollowing actually means
- Removed misleading checklist item about tag fetch defaults changing
- Updated examples to show defaults work identically in both versions

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>
Signed-off-by: Arieh Schneier <15041913+AriehSchneier@users.noreply.github.com>

Author: AriehSchneier

src/tutorials/migrating-from-v5-to-v6.md

@@ -26,7 +26,6 @@ Use this checklist to audit your codebase before upgrading:
 - [ ] Update the module import path from `github.com/go-git/go-git/v5` to `github.com/go-git/go-git/v6`
 - [ ] Call `defer r.Close()` on every `*git.Repository` obtained from filesystem-backed operations
 - [ ] Remove the `isBare bool` positional argument from `git.PlainClone` calls; set `CloneOptions.Bare` instead
-- [ ] Update any explicit `git.AllTags` / tag-fetch logic — tags are **no longer fetched by default** on `Fetch`
 - [ ] Update explicit `git.TagMode` type references to `plumbing.TagMode` (constant usage like `git.AllTags` is unchanged)
 - [ ] Rename `config.Version_0` / `config.Version_1` constants to `config.Version0` / `config.Version1`
 - [ ] Update code that implements or embeds `commitgraph.Index` — the interface gained `io.Closer` and new methods
@@ -110,37 +109,37 @@ r, err := git.PlainClone("/path/to/repo", &git.CloneOptions{
 
 ---
 
-### 3. Tags are no longer fetched by default on `Fetch` ✅ Merged
+### 3. Understanding tag fetch defaults (no change between v5 and v6) ✅ Clarification
 
-**What changed:** `git.FetchOptions` previously defaulted to fetching all
-tags (`AllTags`). In v6 the default is **no tags**. This aligns go-git's
-behaviour with the `git fetch` CLI, which only auto-follows tags
-reachable from fetched commits when no explicit tag refspec is given.
+**What is the default behavior:** Tag fetching defaults have **not changed** between v5 and v6. Both versions use:
+- `CloneOptions.Tags` defaults to `AllTags` (fetch all tags)
+- `FetchOptions.Tags` defaults to `TagFollowing` (fetch tags reachable from fetched commits)
 
-**Why:** When comparing actual `git fetch` behaviour with the test
-expectations in go-git, it became clear that the tests expected all tags to
-be pulled without the user explicitly requesting them.
+**What `TagFollowing` means:** `TagFollowing` fetches tags that point to commits being fetched (matching `git fetch` behavior without explicit tag refspecs). This is different from:
+- `AllTags` — fetch all tags from the remote (like `git fetch --tags`)
+- `NoTags` — fetch no tags at all (like `git fetch --no-tags`)
 
-**Impact:** Code that relied on tags being silently included in every
-`Fetch` call will no longer receive them.
+**Why this section exists:** A test fix in PR #1459 corrected a test that incorrectly expected `AllTags` behavior without setting it. This was not a behavior change—just a test correction.
 
-**How to migrate:** If you need all remote tags, set `Tags: git.AllTags`
-explicitly:
+**Impact:** None. If you were relying on default behavior in v5, it works identically in v6.
+
+**If you need all tags with `Fetch`:** Explicitly set `Tags: git.AllTags`:
 
 ```go
-// v5 — tags were returned by default
+// Both v5 and v6 — default behavior (TagFollowing)
 err := r.Fetch(&git.FetchOptions{
     RemoteName: "origin",
+    // Tags implicitly defaults to TagFollowing
 })
 
-// v6 — must opt in to fetching all tags
+// Both v5 and v6 — fetch ALL tags explicitly
 err := r.Fetch(&git.FetchOptions{
     RemoteName: "origin",
     Tags:       git.AllTags,
 })
 ```
 
-**References:** [PR #1459](https://github.com/go-git/go-git/pull/1459)
+**References:** [PR #1459](https://github.com/go-git/go-git/pull/1459) (test fix, not a behavior change)
 
 ---