"Backup log" is similar to reflog. But instead of keeping track of ref changes, it keeps track of file content changes. These could be from the index (e.g. "git add" replacing something in the index), worktree ("git reset --hard" deleting everything) or in gitdir ("git config --edit", or deleted reflog). Backup log, when enabled, keeps the backup versions so you can undo if needed. Head for 01/24 to have a better picture what it does, when backups are made... This series adds a new plumbing command 'git backup-log' to manage these backups. A couple things left to do: - high level UI design, including maybe extended SHA-1 syntax - whether "git checkout <paths>" should keep backups. I think doing it unconditionally may be too much, but maybe keep backups of files with "precious" attribute on - a UI to edit $GIT_DIR/info/excludes and gitattributes so we can make backups of them - whether we should keep command causing the changes in the backup log (e.g. this change is made by git-add, that one git-rebase...). Reflog has this. I did not add it because it complicates the parsing a bit and not sure if it's worth it. Nguyễn Thái Ngọc Duy (24): doc: introduce new "backup log" concept backup-log: add "update" subcommand read-cache.c: new flag for add_index_entry() to write to backup log add: support backup log update-index: support backup log with --keep-backup commit: support backup log apply: support backup log with --keep-backup add--interactive: support backup log backup-log.c: add API for walking backup log backup-log: add cat command backup-log: add diff command backup-log: add log command backup-log: add prune command gc: prune backup logs backup-log: keep all blob references around sha1-file.c: let index_path() accept NULL istate config --edit: support backup log refs: keep backup of deleted reflog unpack-trees.c: keep backup of ignored files being overwritten reset --hard: keep backup of overwritten files checkout -f: keep backup of overwritten files am: keep backup of overwritten files on --skip or --abort rebase: keep backup of overwritten files on --skip or --abort FIXME .gitignore | 1 + Documentation/config/core.txt | 5 + Documentation/git-apply.txt | 3 + Documentation/git-backup-log.txt | 109 ++++++++ Documentation/git-update-index.txt | 3 + Makefile | 2 + apply.c | 38 ++- apply.h | 1 + backup-log.c | 388 +++++++++++++++++++++++++++++ backup-log.h | 38 +++ builtin.h | 1 + builtin/add.c | 5 + builtin/am.c | 3 + builtin/backup-log.c | 371 +++++++++++++++++++++++++++ builtin/checkout.c | 4 + builtin/commit.c | 16 +- builtin/config.c | 27 +- builtin/gc.c | 3 + builtin/pack-objects.c | 9 +- builtin/rebase.c | 6 +- builtin/repack.c | 1 + builtin/reset.c | 2 + builtin/update-index.c | 7 + cache.h | 2 + command-list.txt | 1 + git-add--interactive.perl | 14 +- git.c | 1 + merge-recursive.c | 2 +- merge.c | 2 + parse-options.c | 2 +- reachable.c | 3 + read-cache.c | 49 +++- refs/files-backend.c | 32 +++ revision.c | 3 + sha1-file.c | 8 +- t/t2080-backup-log.sh | 228 +++++++++++++++++ unpack-trees.c | 143 +++++++++-- unpack-trees.h | 6 +- 38 files changed, 1488 insertions(+), 51 deletions(-) create mode 100644 Documentation/git-backup-log.txt create mode 100644 backup-log.c create mode 100644 backup-log.h create mode 100644 builtin/backup-log.c create mode 100755 t/t2080-backup-log.sh -- 2.20.0.rc2.486.g9832c05c3d