restore.v

1//! Writing a tree back onto disk.2//!3//! A restore writes the target's files and deletes the tracked files the4//! target does not have. An ignored file already on disk is never overwritten5//! or deleted, and every file lands through a temp file and a rename, so an6//! interrupted restore leaves a readable tree rather than half-written files.78module snapshot910import os11import src.storage1213// Set while a restore writes into the repo. A restore records its save first,14// so a mark still here means the files stopped part way: the tree is half one15// save and half another, and nobody's work.16const restoring_key = 'restoring'1718pub const restore_unfinished = 'an earlier restore stopped before all its files were written — run koh revert to finish it (it records the tree as it is in a checkpoint first)'1920pub fn restore_pending(store &storage.Store) bool {21	return store.state(restoring_key) != none22}2324// mark_restore goes down before a restore records its save, so a kill between25// the save and the files still leaves it; restore_files lifts it at the end.26pub fn mark_restore(store &storage.Store) ! {27	store.set_state(restoring_key, 'yes')!28}2930pub fn clear_restore_mark(store &storage.Store) ! {31	store.remove_state(restoring_key)!32}3334pub struct RestoreReport {35pub:36	written int37	removed int38}3940// restore_files writes `target` into the working tree and deletes the paths in41// `remove` (tracked files the target does not have). An ignored file already42// on disk is left as it is, even when the target saved an older copy: it may43// hold work no save has. A missing one is written. Every file lands through a44// temp file and a rename, so an interrupted restore leaves a readable tree45// rather than half-written files.46pub fn restore_files(store &storage.Store, root string, ig Ignore, target []FileEntry, remove []string) !RestoreReport {47	// Peek writes elsewhere; only the repo's own tree carries the mark.48	in_repo := root == store.root49	report := write_tree(store, root, ig, target, remove) or {50		// The save is recorded by now, so the way on is to finish, not retry.51		if in_repo {52			return error('${err.msg()} — the restore stopped part way; fix that, then run koh revert to finish it')53		}54		return err55	}56	if in_repo {57		clear_restore_mark(store)!58	}59	return report60}6162fn write_tree(store &storage.Store, root string, ig Ignore, target []FileEntry, remove []string) !RestoreReport {63	mut wanted := map[string]bool{}64	for entry in target {65		wanted[entry.path] = true66	}67	mut removed := 068	for path in remove {69		full := os.join_path(root, path)70		if !os.is_file(full) || ig.matches(path, false) || path in wanted {71			continue72		}73		os.rm(full)!74		removed++75		prune_empty_dirs(root, os.dir(full))76	}77	// A folder where a file belongs: gone if the removals emptied it, else it78	// holds ignored files, which are never touched. Refuse before writing, as79	// V's move would otherwise drop the file inside the folder.80	for entry in target {81		full := os.join_path(root, entry.path)82		if os.is_dir(full) {83			os.rmdir(full) or {84				return error('${entry.path} is a folder of ignored files where a saved file belongs — move it')85			}86		}87	}88	mut written := 089	cache := store.load_cache()!90	for entry in target {91		if ig.matches(entry.path, false) && os.exists(os.join_path(root, entry.path)) {92			continue93		}94		// Rewriting a file that already matches would only reset its mtime,95		// and make the next status hash it again.96		if already_there(root, entry, cache) {97			continue98		}99		data := store.get_object(entry.hash)!100		write_file(os.join_path(root, entry.path), data, entry.executable)!101		written++102	}103	return RestoreReport{104		written: written105		removed: removed106	}107}108109// already_there reports whether the file on disk has the target's content and110// executable bit. The file cache answers without reading when the file is as111// it was when last hashed.112fn already_there(root string, entry FileEntry, cache map[string]storage.CacheRow) bool {113	full := os.join_path(root, entry.path)114	st := lstat(full) or { return false }115	if st.kind != .file || st.size != entry.size || is_executable(st.mode) != entry.executable {116		return false117	}118	if row := cache[entry.path] {119		if row.size == st.size && row.mtime_ns == st.mtime_ns && row.ctime_ns == st.ctime_ns {120			return row.hash == entry.hash121		}122	}123	data := os.read_bytes(full) or { return false }124	return storage.hash_hex(data) == entry.hash125}126127// check_links refuses a restore that would write through a symlinked folder.128// Koh never follows links, so the folder it points at is not the repo's, and129// writing there would overwrite files outside it. Callers run it before they130// record anything.131pub fn check_links(root string, files []FileEntry) ! {132	for file in files {133		mut folder := ''134		for part in file.path.split('/')#[..-1] {135			folder = if folder == '' { part } else { '${folder}/${part}' }136			st := lstat(os.join_path(root, folder)) or { break }137			if st.kind == .symlink {138				return error('${folder} is a symbolic link where a saved folder belongs — koh will not write through it; move it, then run the command again')139			}140		}141	}142}143144fn write_file(path string, data []u8, executable bool) ! {145	os.mkdir_all(os.dir(path), os.MkdirParams{})!146	tmp := '${path}.koh-tmp-${os.getpid()}'147	os.write_file_array(tmp, data)!148	mode := if executable { 0o755 } else { 0o644 }149	os.chmod(tmp, mode)!150	os.rename(tmp, path)!151}152153// prune_empty_dirs clears directories a restore emptied, never the repo root.154fn prune_empty_dirs(root string, dir string) {155	mut current := dir156	for current.len > root.len && current.starts_with(root) {157		if (os.ls(current) or { return }).len > 0 {158			return159		}160		os.rmdir(current) or { return }161		current = os.dir(current)162	}163}