24 lines
3.0 KiB
Markdown
24 lines
3.0 KiB
Markdown
---
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name: gitflow-back-merge-plumbing
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description: "(HISTORICAL for dank/command-center — switched to trunk-based 2026-10-18, no develop branch.) Back-merge main into develop with pure git plumbing when branch checkout is policy-blocked; avoids the polluted-base evil-merge trap."
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---
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# Git-flow back-merge via plumbing (checkout blocked)
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## Applicability
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The command-center repo retired `develop` on 2026-10-18 (trunk-based; see its AGENTS.md § Trunk-based SDLC). Use this only in repos still running git-flow where a `main -> develop` back-merge must land and branch checkout is forbidden. Never merge while HEAD is a session branch — the merge silently lands on it.
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## Procedure
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1. `git fetch origin` and verify with `git ls-remote --heads`.
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2. Find the CLEAN fork point: `mb=$(git merge-base origin/develop origin/main)`. NEVER build the merge commit with a develop-side that already contains main (e.g. a previous broken merge): merge-base then equals main, main-side looks "unchanged", and stale develop content wins everywhere — a clean rc=0 evil merge. Sanity-trigger: if a merge you expect to conflict resolves rc=0, suspect the base.
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3. Real merge, no worktree: `out=$(git merge-tree --write-tree <clean-dev-tip> origin/main); rc=$?; tree=$(echo "$out"|head -1)`. rc=1 = conflicts; list them from the "Conflicted file info" section (lines starting with a 6-digit mode), NOT from `ls-files -u` in some other worktree.
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4. Resolve in index only: `export GIT_INDEX_FILE=/tmp/idx.$$; git read-tree $tree; git update-index --add --cacheinfo 100644,$(git rev-parse origin/main:<path>),<path>` per conflicted path (pick a side deliberately — say which in the message).
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5. `final=$(git write-tree)`; prove no markers: `git grep -l '^<<<<<<<' "$final"` must be empty (run it correctly — an empty count from a malformed invocation hides markers).
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6. `commit=$(git commit-tree "$final" -p <clean-dev-tip> -p origin/main -m "...")`; `git push --force-with-lease=develop:<current-dev-tip> origin "$commit:develop"` (lease prevents clobbering concurrent pushes; document superseded commits). A back-merge onto an untouched develop is additive — plain push, no lease needed.
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7. Verify ALL of: `git merge-base --is-ancestor origin/main origin/develop`; grep a distinctive merged value in `origin/develop:<file>` (content, not just ancestry); `git diff --stat origin/main origin/develop` matches expectations.
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## Traps
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- `merge-tree` writes conflict markers INTO the tree for conflicted paths — always overwrite every conflicted path before commit-tree.
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- A wrong tree pushed as a merge commit makes every later merge against it resolve "cleanly" to stale content; fix by rebuilding from the clean fork point and force-with-lease, citing the broken commits in the message.
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- Gitea PR merge API needs `Content-Type: application/json` AND `{"Do":"merge"}` in the BODY (query param alone 422s); a 405 "Please try again later" right after the base branch moved is transient mergeability recomputation — wait a few seconds and retry.
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