builtin: add new "history" command

When rewriting history via git-rebase(1) there are a few very common use
cases:

  - The ordering of two commits should be reversed.

  - A commit should be split up into two commits.

  - A commit should be dropped from the history completely.

  - Multiple commits should be squashed into one.

  - Editing an existing commit that is not the tip of the current
    branch.

While these operations are all doable, it often feels needlessly kludgey
to do so by doing an interactive rebase, using the editor to say what
one wants, and then perform the actions. Also, some operations like
splitting up a commit into two are way more involved than that and
require a whole series of commands.

Rebases also do not update dependent branches. The use of stacked
branches has grown quite common with competing version control systems
like Jujutsu though, so it clearly is a need that users have. While
rebases _can_ serve this use case if one always works on the latest
stacked branch, it is somewhat awkward and very easy to get wrong.

Add a new "history" command to plug these gaps. This command will have
several different subcommands to imperatively rewrite history for common
use cases like the above.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/.gitignore b/.gitignore
index 78a45cb..24635cf 100644 (file)
--- a/.gitignore
+++ b/.gitignore
@@ -79,6 +79,7 @@
 /git-grep
 /git-hash-object
 /git-help
+/git-history
 /git-hook
 /git-http-backend
 /git-http-fetch

diff --git a/Documentation/git-history.adoc b/Documentation/git-history.adoc
new file mode 100644 (file)
index 0000000..68c35f3
--- /dev/null
+++ b/Documentation/git-history.adoc
@@ -0,0 +1,57 @@
+git-history(1)
+==============
+
+NAME
+----
+git-history - EXPERIMENTAL: Rewrite history
+
+SYNOPSIS
+--------
+[synopsis]
+git history [<options>]
+
+DESCRIPTION
+-----------
+
+Rewrite history by rearranging or modifying specific commits in the
+history.
+
+THIS COMMAND IS EXPERIMENTAL. THE BEHAVIOR MAY CHANGE.
+
+This command is related to linkgit:git-rebase[1] in that both commands can be
+used to rewrite history. There are a couple of major differences though:
+
+* linkgit:git-history[1] can work in a bare repository as it does not need to
+  touch either the index or the worktree.
+* linkgit:git-history[1] does not execute any linkgit:githooks[5] at the
+  current point in time. This may change in the future.
+* linkgit:git-history[1] by default updates all branches that are descendants
+  of the original commit to point to the rewritten commit.
+
+Overall, linkgit:git-history[1] aims to provide a more opinionated way to modify
+your commit history that is simpler to use compared to linkgit:git-rebase[1] in
+general.
+
+Use linkgit:git-rebase[1] if you want to reapply a range of commits onto a
+different base, or interactive rebases if you want to edit a range of commits
+at once.
+
+LIMITATIONS
+-----------
+
+This command does not (yet) work with histories that contain merges. You
+should use linkgit:git-rebase[1] with the `--rebase-merges` flag instead.
+
+Furthermore, the command does not support operations that can result in merge
+conflicts. This limitation is by design as history rewrites are not intended to
+be stateful operations. The limitation can be lifted once (if) Git learns about
+first-class conflicts.
+
+COMMANDS
+--------
+
+No commands are supported yet.
+
+GIT
+---
+Part of the linkgit:git[1] suite

diff --git a/Documentation/meson.build b/Documentation/meson.build
index f02dbc2..fd2e8cc 100644 (file)
--- a/Documentation/meson.build
+++ b/Documentation/meson.build
@@ -64,6 +64,7 @@ manpages = {
   'git-gui.adoc' : 1,
   'git-hash-object.adoc' : 1,
   'git-help.adoc' : 1,
+  'git-history.adoc' : 1,
   'git-hook.adoc' : 1,
   'git-http-backend.adoc' : 1,
   'git-http-fetch.adoc' : 1,

diff --git a/Makefile b/Makefile
index 1c64a5d..c0569ed 100644 (file)
--- a/Makefile
+++ b/Makefile
@@ -1418,6 +1418,7 @@ BUILTIN_OBJS += builtin/get-tar-commit-id.o
 BUILTIN_OBJS += builtin/grep.o
 BUILTIN_OBJS += builtin/hash-object.o
 BUILTIN_OBJS += builtin/help.o
+BUILTIN_OBJS += builtin/history.o
 BUILTIN_OBJS += builtin/hook.o
 BUILTIN_OBJS += builtin/index-pack.o
 BUILTIN_OBJS += builtin/init-db.o

diff --git a/builtin.h b/builtin.h
index 1b35565..93c91d0 100644 (file)
--- a/builtin.h
+++ b/builtin.h
@@ -172,6 +172,7 @@ int cmd_get_tar_commit_id(int argc, const char **argv, const char *prefix, struc
 int cmd_grep(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_hash_object(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_help(int argc, const char **argv, const char *prefix, struct repository *repo);
+int cmd_history(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_hook(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_index_pack(int argc, const char **argv, const char *prefix, struct repository *repo);
 int cmd_init_db(int argc, const char **argv, const char *prefix, struct repository *repo);

diff --git a/builtin/history.c b/builtin/history.c
new file mode 100644 (file)
index 0000000..f6fe326
--- /dev/null
+++ b/builtin/history.c
@@ -0,0 +1,22 @@
+#include "builtin.h"
+#include "gettext.h"
+#include "parse-options.h"
+
+int cmd_history(int argc,
+               const char **argv,
+               const char *prefix,
+               struct repository *repo UNUSED)
+{
+       const char * const usage[] = {
+               N_("git history [<options>]"),
+               NULL,
+       };
+       struct option options[] = {
+               OPT_END(),
+       };
+
+       argc = parse_options(argc, argv, prefix, options, usage, 0);
+       if (argc)
+               usagef("unrecognized argument: %s", argv[0]);
+       return 0;
+}

diff --git a/command-list.txt b/command-list.txt
index accd3d0..f9005cf 100644 (file)
--- a/command-list.txt
+++ b/command-list.txt
@@ -115,6 +115,7 @@ git-grep                                mainporcelain           info
 git-gui                                 mainporcelain
 git-hash-object                         plumbingmanipulators
 git-help                                ancillaryinterrogators          complete
+git-history                             mainporcelain           history
 git-hook                                purehelpers
 git-http-backend                        synchingrepositories
 git-http-fetch                          synchelpers

diff --git a/git.c b/git.c
index c5fad56..744cb65 100644 (file)
--- a/git.c
+++ b/git.c
@@ -586,6 +586,7 @@ static struct cmd_struct commands[] = {
        { "grep", cmd_grep, RUN_SETUP_GENTLY },
        { "hash-object", cmd_hash_object },
        { "help", cmd_help },
+       { "history", cmd_history, RUN_SETUP },
        { "hook", cmd_hook, RUN_SETUP },
        { "index-pack", cmd_index_pack, RUN_SETUP_GENTLY | NO_PARSEOPT },
        { "init", cmd_init_db },

diff --git a/meson.build b/meson.build
index a5a4e99..3a1d12c 100644 (file)
--- a/meson.build
+++ b/meson.build
@@ -610,6 +610,7 @@ builtin_sources = [
   'builtin/grep.c',
   'builtin/hash-object.c',
   'builtin/help.c',
+  'builtin/history.c',
   'builtin/hook.c',
   'builtin/index-pack.c',
   'builtin/init-db.c',

diff --git a/t/meson.build b/t/meson.build
index 459c52a..73006b0 100644 (file)
--- a/t/meson.build
+++ b/t/meson.build
@@ -387,6 +387,7 @@ integration_tests = [
   't3436-rebase-more-options.sh',
   't3437-rebase-fixup-options.sh',
   't3438-rebase-broken-files.sh',
+  't3450-history.sh',
   't3500-cherry.sh',
   't3501-revert-cherry-pick.sh',
   't3502-cherry-pick-merge.sh',

diff --git a/t/t3450-history.sh b/t/t3450-history.sh
new file mode 100755 (executable)
index 0000000..417c343
--- /dev/null
+++ b/t/t3450-history.sh
@@ -0,0 +1,17 @@
+#!/bin/sh
+
+test_description='tests for git-history command'
+
+. ./test-lib.sh
+
+test_expect_success 'does nothing without any arguments' '
+       git history >out 2>&1 &&
+       test_must_be_empty out
+'
+
+test_expect_success 'raises an error with unknown argument' '
+       test_must_fail git history garbage 2>err &&
+       test_grep "unrecognized argument: garbage" err
+'
+
+test_done