patches: MAME is now pushed as a full repo (branch vt1200-local) -- correct the README, which said it was not, and say why the patch is still kept

patches/README.md

@@ -31,23 +31,34 @@ because upstream moved, `git apply -3` will fall back to a three-way merge.
 `mame0289` is a tag leaves a **detached HEAD**, so commit before you check
 anything else out — otherwise edits are discarded.
 
-## Why a patch and not a mirror
+## Why a patch as well as a repo
 
-The MAME tree is not pushed as a repository. Its remote **rejects shallow
-updates** (`receive.shallowUpdate` is off), and this is a `--depth 1` clone
-pinned at a tag, so no push from it is accepted:
+The MAME tree **is** now pushed as a full repository — `origin` is
+`git@git.k-space.ee:arti/mame0289.git`, and our commit sits on branch
+**`vt1200-local`** there. Getting there needed `git fetch --unshallow` first
+(99,645 commits, `.git` 1.9 GB, ~3 minutes) because the server rejects shallow
+updates:
 
 ```
 ! [remote rejected] vt1200-local -> vt1200-local (shallow update not allowed)
 ```
 
-Making it pushable means `git fetch --unshallow`, which downloads MAME's **full
-history** — several GB and tens of minutes — to transmit a 50-line difference.
-This patch carries the same information in 155 lines and is reviewable in a diff.
+`receive.shallowUpdate` is off on that server, and the clone was `--depth 1`
+pinned at a tag, so no push from it was accepted until it was unshallowed.
+`git config receive.shallowUpdate true` on the server would avoid the unshallow
+for anyone repeating this.
 
-If a real fork is wanted anyway, unshallow first:
+This patch is kept anyway, for three reasons:
+
+* it is the **complete change in 50 lines** — reviewable in a diff, where a
+  1.9 GB repository is not;
+* it **reproduces the tree without a full clone**, which matters on a fresh
+  machine or a slow link;
+* it is the **record of what this project changes about upstream MAME**, and
+  every claim about those changes lives beside the driver rather than in a
+  repository's history.
+
+Note the branch name is `vt1200-local`, not `master`. If the forge's default
+branch is still `master` and therefore empty, set `vt1200-local` as the default
+so the repository opens on something.
 
-```sh
-git -C /home/arti/code/k-space/mame0289 fetch --unshallow upstream
-git -C /home/arti/code/k-space/mame0289 push -u origin vt1200-local
-```