leewc · April 28, 2026 21:29 · leewc · Apr 28, 2026
diff --git a/git-convert-hash.sh b/git-convert-hash.sh
 #!/usr/bin/env bash
 # Toggle a git repo between SHA-1 and SHA-256 object formats.
 # Usage: git-convert-hash.sh [repo-path]
 set -euo pipefail

 REPO="${1:-.}"
 cd "$REPO"

 if [[ ! -d .git ]]; then
  echo "Error: $PWD is not a git repository"
  exit 1
 fi

 CURRENT=$(git rev-parse --show-object-format)
 if [[ "$CURRENT" == "sha256" ]]; then TARGET="sha1"; else TARGET="sha256"; fi

 BRANCH=$(git branch --show-current)
 REMOTE_URL=$(git remote get-url origin 2>/dev/null || true)
 EXPORT_FILE=$(mktemp /tmp/git-export-XXXXXX.fi)
 BACKUP_DIR="${REPO}/.git.backup-$(date +%Y%m%d%H%M%S)"

 echo "Converting $PWD from $CURRENT -> $TARGET"
 echo "Branch: $BRANCH"
 echo "Remote: ${REMOTE_URL:-none}"
 echo "Backup: $BACKUP_DIR"
 echo ""

 # Backup
 cp -r "$REPO/.git" "$BACKUP_DIR"
 echo "✓ Backed up .git to $BACKUP_DIR"

 # Export
 git fast-export --all --signed-tags=strip > "$EXPORT_FILE"
 echo "✓ Exported history to $EXPORT_FILE"

 # Reinit
 rm -rf .git
 git init --object-format="$TARGET" -b "$BRANCH"
 echo "✓ Reinitialized as $TARGET"

 # Import
 git fast-import < "$EXPORT_FILE"
 echo "✓ Imported history"

 # Restore working tree
 git checkout -f "$BRANCH"
 echo "✓ Checked out $BRANCH"

 # Restore remote
 if [[ -n "$REMOTE_URL" ]]; then
  git remote add origin "$REMOTE_URL"
  echo "✓ Restored remote origin -> $REMOTE_URL"
 fi

 # Cleanup
 rm -f "$EXPORT_FILE"

 echo ""
 echo "Done! Verify with:"
 echo "  git log --oneline"
 echo "  git status"
 echo ""
 echo "=== SYNCING WITH REMOTE ==="
 echo ""
 echo "Since all commit hashes changed, you have two options:"
 echo ""
 echo "Option 1: Force push from this local copy (if you have push access):"
 echo "  git push --force --all"
 echo "  git push --force --tags"
 echo ""
 echo "Option 2: If the remote was ALSO converted separately (e.g. GitLab"
 echo "  converted the repo), the remote has new hashes too. In that case,"
 echo "  follow these steps:"
 echo ""
 echo "  # 1. Fetch the new remote history (don't pull!)"
 echo "  git fetch origin"
 echo ""
 echo "  # 2. Set upstream tracking"
 echo "  git branch --set-upstream-to=origin/$BRANCH $BRANCH"
 echo ""
 echo "  # 3. Rebase your local commits onto the new remote history"
 echo "  git rebase --onto origin/$BRANCH --root"
 echo ""
 echo "  # 4. Resolve any conflicts (prefer your version for files you own)"
 echo "  #    git checkout --theirs <file>  # take your version"
 echo "  #    git add <file>"
 echo "  #    git rebase --continue"
 echo ""
 echo "  # 5. Push"
 echo "  git push"
 echo ""
 echo "  ⚠️  Do NOT use 'git pull' or 'git pull -Xours/-Xtheirs'!"
 echo "  The histories have no common ancestor, so a merge/pull will"
 echo "  silently discard your commit history. If you already did this,"
 echo "  your commits are still in the reflog:"
 echo ""
 echo "  git reflog                          # find your old HEAD"
 echo "  git cherry-pick <oldest>..<newest>  # replay them on top"
 echo ""
 if [[ -z "$REMOTE_URL" ]]; then
  echo "No remote was configured. To add one:"
  echo "  git remote add origin <url>"
  echo "  git push -u origin $BRANCH"
  echo ""
 fi
 echo "Backup at: $BACKUP_DIR (remove when satisfied)"
	#!/usr/bin/env bash
	# Toggle a git repo between SHA-1 and SHA-256 object formats.
	# Usage: git-convert-hash.sh [repo-path]
	set -euo pipefail

	REPO="${1:-.}"
	cd "$REPO"

	if [[ ! -d .git ]]; then
	echo "Error: $PWD is not a git repository"
	exit 1
	fi

	CURRENT=$(git rev-parse --show-object-format)
	if [[ "$CURRENT" == "sha256" ]]; then TARGET="sha1"; else TARGET="sha256"; fi

	BRANCH=$(git branch --show-current)
	REMOTE_URL=$(git remote get-url origin 2>/dev/null \|\| true)
	EXPORT_FILE=$(mktemp /tmp/git-export-XXXXXX.fi)
	BACKUP_DIR="${REPO}/.git.backup-$(date +%Y%m%d%H%M%S)"

	echo "Converting $PWD from $CURRENT -> $TARGET"
	echo "Branch: $BRANCH"
	echo "Remote: ${REMOTE_URL:-none}"
	echo "Backup: $BACKUP_DIR"
	echo ""

	# Backup
	cp -r "$REPO/.git" "$BACKUP_DIR"
	echo "✓ Backed up .git to $BACKUP_DIR"

	# Export
	git fast-export --all --signed-tags=strip > "$EXPORT_FILE"
	echo "✓ Exported history to $EXPORT_FILE"

	# Reinit
	rm -rf .git
	git init --object-format="$TARGET" -b "$BRANCH"
	echo "✓ Reinitialized as $TARGET"

	# Import
	git fast-import < "$EXPORT_FILE"
	echo "✓ Imported history"

	# Restore working tree
	git checkout -f "$BRANCH"
	echo "✓ Checked out $BRANCH"

	# Restore remote
	if [[ -n "$REMOTE_URL" ]]; then
	git remote add origin "$REMOTE_URL"
	echo "✓ Restored remote origin -> $REMOTE_URL"
	fi

	# Cleanup
	rm -f "$EXPORT_FILE"

	echo ""
	echo "Done! Verify with:"
	echo " git log --oneline"
	echo " git status"
	echo ""
	echo "=== SYNCING WITH REMOTE ==="
	echo ""
	echo "Since all commit hashes changed, you have two options:"
	echo ""
	echo "Option 1: Force push from this local copy (if you have push access):"
	echo " git push --force --all"
	echo " git push --force --tags"
	echo ""
	echo "Option 2: If the remote was ALSO converted separately (e.g. GitLab"
	echo " converted the repo), the remote has new hashes too. In that case,"
	echo " follow these steps:"
	echo ""
	echo " # 1. Fetch the new remote history (don't pull!)"
	echo " git fetch origin"
	echo ""
	echo " # 2. Set upstream tracking"
	echo " git branch --set-upstream-to=origin/$BRANCH $BRANCH"
	echo ""
	echo " # 3. Rebase your local commits onto the new remote history"
	echo " git rebase --onto origin/$BRANCH --root"
	echo ""
	echo " # 4. Resolve any conflicts (prefer your version for files you own)"
	echo " # git checkout --theirs <file> # take your version"
	echo " # git add <file>"
	echo " # git rebase --continue"
	echo ""
	echo " # 5. Push"
	echo " git push"
	echo ""
	echo " ⚠️ Do NOT use 'git pull' or 'git pull -Xours/-Xtheirs'!"
	echo " The histories have no common ancestor, so a merge/pull will"
	echo " silently discard your commit history. If you already did this,"
	echo " your commits are still in the reflog:"
	echo ""
	echo " git reflog # find your old HEAD"
	echo " git cherry-pick <oldest>..<newest> # replay them on top"
	echo ""
	if [[ -z "$REMOTE_URL" ]]; then
	echo "No remote was configured. To add one:"
	echo " git remote add origin <url>"
	echo " git push -u origin $BRANCH"
	echo ""
	fi
	echo "Backup at: $BACKUP_DIR (remove when satisfied)"
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