Re: [RFC PATCH 4/7] autostash: extract reset_head() from rebase

> Hi Denton
>
> It's great to see this being libified, I've had it in mind to do this so we
> can avoid forking 'git checkout' in sequencer.c
>
> On 16/10/2019 18:26, Denton Liu wrote:
> > Begin the process of lib-ifying the autostash code. In a future commit,
> >
> > This patch is best viewed with `--color-moved` and
> > `--color-moved-ws=allow-indentation-change`.
> > this will be used to implement `--autostash` in other builtins.
> >
> > Signed-off-by: Denton Liu <liu.denton@gmail.com>
> > ---
> >   autostash.c      | 137 +++++++++++++++++++++++++++++++++++++++++++++++
> >   autostash.h      |  12 +++++
> >   builtin/rebase.c | 137 -----------------------------------------------
> >   3 files changed, 149 insertions(+), 137 deletions(-)
> >
> > diff --git a/autostash.c b/autostash.c
> > index 62ec7a7c80..eb58e0c8a4 100644
> > --- a/autostash.c
> > +++ b/autostash.c
> > @@ -1,9 +1,17 @@
> > +#define USE_THE_INDEX_COMPATIBILITY_MACROS
>
> It might be nicer to have a preparatory step that fixes this by adding a
> 'struct repository *r' argument to the function in builtin/rebase.c before
> moving the function. You could also do the same for next patch and then move
> both functions together.

>
> Best Wishes
>
> Phillip
>
> > +
> >   #include "git-compat-util.h"
> >   #include "autostash.h"
> > +#include "cache-tree.h"
> >   #include "dir.h"
> >   #include "gettext.h"
> > +#include "lockfile.h"
> > +#include "refs.h"
> >   #include "run-command.h"
> >   #include "strbuf.h"
> > +#include "tree-walk.h"
> > +#include "tree.h"
> > +#include "unpack-trees.h"
> >
> >   int read_one(const char *path, struct strbuf *buf)
> >   {
> > @@ -13,6 +21,135 @@ int read_one(const char *path, struct strbuf *buf)
> >   	return 0;
> >   }
> >
> > +int reset_head(struct object_id *oid, const char *action,
> > +	       const char *switch_to_branch, unsigned flags,
> > +	       const char *reflog_orig_head, const char *reflog_head)
> > +{
> > +	unsigned detach_head = flags & RESET_HEAD_DETACH;
> > +	unsigned reset_hard = flags & RESET_HEAD_HARD;
> > +	unsigned run_hook = flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
> > +	unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
> > +	unsigned update_orig_head = flags & RESET_ORIG_HEAD;
> > +	struct object_id head_oid;
> > +	struct tree_desc desc[2] = { { NULL }, { NULL } };
> > +	struct lock_file lock = LOCK_INIT;
> > +	struct unpack_trees_options unpack_tree_opts;
> > +	struct tree *tree;
> > +	const char *reflog_action;
> > +	struct strbuf msg = STRBUF_INIT;
> > +	size_t prefix_len;
> > +	struct object_id *orig = NULL, oid_orig,
> > +		*old_orig = NULL, oid_old_orig;
> > +	int ret = 0, nr = 0;
> > +
> > +	if (switch_to_branch && !starts_with(switch_to_branch, "refs/"))
> > +		BUG("Not a fully qualified branch: '%s'", switch_to_branch);
> > +
> > +	if (!refs_only && hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
> > {
> > +		ret = -1;
> > +		goto leave_reset_head;
> > +	}
> > +
> > +	if ((!oid || !reset_hard) && get_oid("HEAD", &head_oid)) {
> > +		ret = error(_("could not determine HEAD revision"));
> > +		goto leave_reset_head;
> > +	}
> > +
> > +	if (!oid)
> > +		oid = &head_oid;
> > +
> > +	if (refs_only)
> > +		goto reset_head_refs;
> > +
> > +	memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
> > +	setup_unpack_trees_porcelain(&unpack_tree_opts, action);
> > +	unpack_tree_opts.head_idx = 1;
> > +	unpack_tree_opts.src_index = the_repository->index;
> > +	unpack_tree_opts.dst_index = the_repository->index;
> > +	unpack_tree_opts.fn = reset_hard ? oneway_merge : twoway_merge;
> > +	unpack_tree_opts.update = 1;
> > +	unpack_tree_opts.merge = 1;
> > +	if (!detach_head)
> > +		unpack_tree_opts.reset = 1;
> > +
> > +	if (repo_read_index_unmerged(the_repository) < 0) {
> > +		ret = error(_("could not read index"));
> > +		goto leave_reset_head;
> > +	}
> > +
> > +	if (!reset_hard && !fill_tree_descriptor(the_repository, &desc[nr++],
> > &head_oid)) {
> > +		ret = error(_("failed to find tree of %s"),
> > +			    oid_to_hex(&head_oid));
> > +		goto leave_reset_head;
> > +	}
> > +
> > +	if (!fill_tree_descriptor(the_repository, &desc[nr++], oid)) {
> > +		ret = error(_("failed to find tree of %s"), oid_to_hex(oid));
> > +		goto leave_reset_head;
> > +	}
> > +
> > +	if (unpack_trees(nr, desc, &unpack_tree_opts)) {
> > +		ret = -1;
> > +		goto leave_reset_head;
> > +	}
> > +
> > +	tree = parse_tree_indirect(oid);
> > +	prime_cache_tree(the_repository, the_repository->index, tree);
> > +
> > +	if (write_locked_index(the_repository->index, &lock, COMMIT_LOCK) < 0)
> > {
> > +		ret = error(_("could not write index"));
> > +		goto leave_reset_head;
> > +	}
> > +
> > +reset_head_refs:
> > +	reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
> > +	strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : "rebase");
> > +	prefix_len = msg.len;
> > +
> > +	if (update_orig_head) {
> > +		if (!get_oid("ORIG_HEAD", &oid_old_orig))
> > +			old_orig = &oid_old_orig;
> > +		if (!get_oid("HEAD", &oid_orig)) {
> > +			orig = &oid_orig;
> > +			if (!reflog_orig_head) {
> > +				strbuf_addstr(&msg, "updating ORIG_HEAD");
> > +				reflog_orig_head = msg.buf;
> > +			}
> > +			update_ref(reflog_orig_head, "ORIG_HEAD", orig,
> > +				   old_orig, 0, UPDATE_REFS_MSG_ON_ERR);
> > +		} else if (old_orig)
> > +			delete_ref(NULL, "ORIG_HEAD", old_orig, 0);
> > +	}
> > +
> > +	if (!reflog_head) {
> > +		strbuf_setlen(&msg, prefix_len);
> > +		strbuf_addstr(&msg, "updating HEAD");
> > +		reflog_head = msg.buf;
> > +	}
> > +	if (!switch_to_branch)
> > +		ret = update_ref(reflog_head, "HEAD", oid, orig,
> > +				 detach_head ? REF_NO_DEREF : 0,
> > +				 UPDATE_REFS_MSG_ON_ERR);
> > +	else {
> > +		ret = update_ref(reflog_head, switch_to_branch, oid,
> > +				 NULL, 0, UPDATE_REFS_MSG_ON_ERR);
> > +		if (!ret)
> > +			ret = create_symref("HEAD", switch_to_branch,
> > +					    reflog_head);
> > +	}
> > +	if (run_hook)
> > +		run_hook_le(NULL, "post-checkout",
> > +			    oid_to_hex(orig ? orig : &null_oid),
> > +			    oid_to_hex(oid), "1", NULL);
> > +
> > +leave_reset_head:
> > +	strbuf_release(&msg);
> > +	rollback_lock_file(&lock);
> > +	while (nr)
> > +		free((void *)desc[--nr].buffer);
> > +	return ret;
> > +}
> > +
> >   int apply_autostash(const char *path)
> >   {
> >   	struct strbuf autostash = STRBUF_INIT;
> > diff --git a/autostash.h b/autostash.h
> > index 5f4e4bd22c..1406638166 100644
> > --- a/autostash.h
> > +++ b/autostash.h
> > @@ -6,6 +6,18 @@
> >   /* Read one file, then strip line endings */
> >   int read_one(const char *path, struct strbuf *buf);
> >
> > +#define GIT_REFLOG_ACTION_ENVIRONMENT "GIT_REFLOG_ACTION"
> > +
> > +#define RESET_HEAD_DETACH (1<<0)
> > +#define RESET_HEAD_HARD (1<<1)
> > +#define RESET_HEAD_RUN_POST_CHECKOUT_HOOK (1<<2)
> > +#define RESET_HEAD_REFS_ONLY (1<<3)
> > +#define RESET_ORIG_HEAD (1<<4)
> > +
> > +int reset_head(struct object_id *oid, const char *action,
> > +	       const char *switch_to_branch, unsigned flags,
> > +	       const char *reflog_orig_head, const char *reflog_head);
> > +
> >   int apply_autostash(const char *path);
> >
> >   #endif
> > diff --git a/builtin/rebase.c b/builtin/rebase.c
> > index 661928d427..c3165896cc 100644
> > --- a/builtin/rebase.c
> > +++ b/builtin/rebase.c
> > @@ -734,143 +734,6 @@ static void add_var(struct strbuf *buf, const char
> > *name, const char *value)
> >   	}
> >   }
> >
> > -#define GIT_REFLOG_ACTION_ENVIRONMENT "GIT_REFLOG_ACTION"
> > -
> > -#define RESET_HEAD_DETACH (1<<0)
> > -#define RESET_HEAD_HARD (1<<1)
> > -#define RESET_HEAD_RUN_POST_CHECKOUT_HOOK (1<<2)
> > -#define RESET_HEAD_REFS_ONLY (1<<3)
> > -#define RESET_ORIG_HEAD (1<<4)
> > -
> > -static int reset_head(struct object_id *oid, const char *action,
> > -		      const char *switch_to_branch, unsigned flags,
> > -		      const char *reflog_orig_head, const char *reflog_head)
> > -{
> > -	unsigned detach_head = flags & RESET_HEAD_DETACH;
> > -	unsigned reset_hard = flags & RESET_HEAD_HARD;
> > -	unsigned run_hook = flags & RESET_HEAD_RUN_POST_CHECKOUT_HOOK;
> > -	unsigned refs_only = flags & RESET_HEAD_REFS_ONLY;
> > -	unsigned update_orig_head = flags & RESET_ORIG_HEAD;
> > -	struct object_id head_oid;
> > -	struct tree_desc desc[2] = { { NULL }, { NULL } };
> > -	struct lock_file lock = LOCK_INIT;
> > -	struct unpack_trees_options unpack_tree_opts;
> > -	struct tree *tree;
> > -	const char *reflog_action;
> > -	struct strbuf msg = STRBUF_INIT;
> > -	size_t prefix_len;
> > -	struct object_id *orig = NULL, oid_orig,
> > -		*old_orig = NULL, oid_old_orig;
> > -	int ret = 0, nr = 0;
> > -
> > -	if (switch_to_branch && !starts_with(switch_to_branch, "refs/"))
> > -		BUG("Not a fully qualified branch: '%s'", switch_to_branch);
> > -
> > -	if (!refs_only && hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
> > {
> > -		ret = -1;
> > -		goto leave_reset_head;
> > -	}
> > -
> > -	if ((!oid || !reset_hard) && get_oid("HEAD", &head_oid)) {
> > -		ret = error(_("could not determine HEAD revision"));
> > -		goto leave_reset_head;
> > -	}
> > -
> > -	if (!oid)
> > -		oid = &head_oid;
> > -
> > -	if (refs_only)
> > -		goto reset_head_refs;
> > -
> > -	memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
> > -	setup_unpack_trees_porcelain(&unpack_tree_opts, action);
> > -	unpack_tree_opts.head_idx = 1;
> > -	unpack_tree_opts.src_index = the_repository->index;
> > -	unpack_tree_opts.dst_index = the_repository->index;
> > -	unpack_tree_opts.fn = reset_hard ? oneway_merge : twoway_merge;
> > -	unpack_tree_opts.update = 1;
> > -	unpack_tree_opts.merge = 1;
> > -	if (!detach_head)
> > -		unpack_tree_opts.reset = 1;
> > -
> > -	if (repo_read_index_unmerged(the_repository) < 0) {
> > -		ret = error(_("could not read index"));
> > -		goto leave_reset_head;
> > -	}
> > -
> > -	if (!reset_hard && !fill_tree_descriptor(the_repository, &desc[nr++],
> > &head_oid)) {
> > -		ret = error(_("failed to find tree of %s"),
> > -			    oid_to_hex(&head_oid));
> > -		goto leave_reset_head;
> > -	}
> > -
> > -	if (!fill_tree_descriptor(the_repository, &desc[nr++], oid)) {
> > -		ret = error(_("failed to find tree of %s"), oid_to_hex(oid));
> > -		goto leave_reset_head;
> > -	}
> > -
> > -	if (unpack_trees(nr, desc, &unpack_tree_opts)) {
> > -		ret = -1;
> > -		goto leave_reset_head;
> > -	}
> > -
> > -	tree = parse_tree_indirect(oid);
> > -	prime_cache_tree(the_repository, the_repository->index, tree);
> > -
> > -	if (write_locked_index(the_repository->index, &lock, COMMIT_LOCK) < 0)
> > {
> > -		ret = error(_("could not write index"));
> > -		goto leave_reset_head;
> > -	}
> > -
> > -reset_head_refs:
> > -	reflog_action = getenv(GIT_REFLOG_ACTION_ENVIRONMENT);
> > -	strbuf_addf(&msg, "%s: ", reflog_action ? reflog_action : "rebase");
> > -	prefix_len = msg.len;
> > -
> > -	if (update_orig_head) {
> > -		if (!get_oid("ORIG_HEAD", &oid_old_orig))
> > -			old_orig = &oid_old_orig;
> > -		if (!get_oid("HEAD", &oid_orig)) {
> > -			orig = &oid_orig;
> > -			if (!reflog_orig_head) {
> > -				strbuf_addstr(&msg, "updating ORIG_HEAD");
> > -				reflog_orig_head = msg.buf;
> > -			}
> > -			update_ref(reflog_orig_head, "ORIG_HEAD", orig,
> > -				   old_orig, 0, UPDATE_REFS_MSG_ON_ERR);
> > -		} else if (old_orig)
> > -			delete_ref(NULL, "ORIG_HEAD", old_orig, 0);
> > -	}
> > -
> > -	if (!reflog_head) {
> > -		strbuf_setlen(&msg, prefix_len);
> > -		strbuf_addstr(&msg, "updating HEAD");
> > -		reflog_head = msg.buf;
> > -	}
> > -	if (!switch_to_branch)
> > -		ret = update_ref(reflog_head, "HEAD", oid, orig,
> > -				 detach_head ? REF_NO_DEREF : 0,
> > -				 UPDATE_REFS_MSG_ON_ERR);
> > -	else {
> > -		ret = update_ref(reflog_head, switch_to_branch, oid,
> > -				 NULL, 0, UPDATE_REFS_MSG_ON_ERR);
> > -		if (!ret)
> > -			ret = create_symref("HEAD", switch_to_branch,
> > -					    reflog_head);
> > -	}
> > -	if (run_hook)
> > -		run_hook_le(NULL, "post-checkout",
> > -			    oid_to_hex(orig ? orig : &null_oid),
> > -			    oid_to_hex(oid), "1", NULL);
> > -
> > -leave_reset_head:
> > -	strbuf_release(&msg);
> > -	rollback_lock_file(&lock);
> > -	while (nr)
> > -		free((void *)desc[--nr].buffer);
> > -	return ret;
> > -}
> > -
> >   static int move_to_original_branch(struct rebase_options *opts)
> >   {
> >    struct strbuf orig_head_reflog = STRBUF_INIT, head_reflog = STRBUF_INIT;
> >
>