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pull: implement pulling into an unborn branch

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b4dc085 (pull: merge into unborn by fast-forwarding from empty
tree, 2013-06-20) established git-pull's current behavior of pulling
into an unborn branch by fast-forwarding the work tree from an empty
tree to the merge head, then setting HEAD to the merge head.

Re-implement this behavior by introducing pull_into_void() which will be
called instead of run_merge() if HEAD is invalid.

Helped-by: Stephen Robin <stephen.robin@gmail.com>
Signed-off-by: Paul Tan <pyokagan@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Paul Tan 2015-06-18 18:54:06 +08:00 committed by Junio C Hamano
parent fe911b8ca0
commit 49ec402d52
1 changed files with 28 additions and 1 deletions
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29
builtin/pull.c
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@ -13,6 +13,7 @@
#include "sha1-array.h"
#include "remote.h"
#include "dir.h"
#include "refs.h"
static const char * const pull_usage[] = {
N_("git pull [options] [<repository> [<refspec>...]]"),
@ -367,6 +368,27 @@ static int run_fetch(const char *repo, const char **refspecs)
return ret;
}
/**
* "Pulls into void" by branching off merge_head.
*/
static int pull_into_void(const unsigned char *merge_head,
const unsigned char *curr_head)
{
/*
* Two-way merge: we treat the index as based on an empty tree,
* and try to fast-forward to HEAD. This ensures we will not lose
* index/worktree changes that the user already made on the unborn
* branch.
*/
if (checkout_fast_forward(EMPTY_TREE_SHA1_BIN, merge_head, 0))
return 1;
if (update_ref("initial pull", "HEAD", merge_head, curr_head, 0, UPDATE_REFS_DIE_ON_ERR))
return 1;
return 0;
}
/**
* Runs git-merge, returning its exit status.
*/
@ -476,5 +498,10 @@ int cmd_pull(int argc, const char **argv, const char *prefix)
if (!merge_heads.nr)
die_no_merge_candidates(repo, refspecs);
return run_merge();
if (is_null_sha1(orig_head)) {
if (merge_heads.nr > 1)
die(_("Cannot merge multiple branches into empty head."));
return pull_into_void(*merge_heads.sha1, curr_head);
} else
return run_merge();
}