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rebase: learn to rebase root commit
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Teach git-rebase a new option --root, which instructs it to rebase the
entire history leading up to <branch>.  This option must be used with
--onto <newbase>, and causes commits that already exist in <newbase>
to be skipped.  (Normal operation skips commits that already exist in
<upstream> instead.)

One possible use-case is with git-svn: suppose you start hacking
(perhaps offline) on a new project, but later notice you want to
commit this work to SVN.  You will have to rebase the entire history,
including the root commit, on a (possibly empty) commit coming from
git-svn, to establish a history connection.  This previously had to
be done by cherry-picking the root commit manually.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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@trast @gitster
trast authored and gitster committed Jan 12, 2009
1 parent d8fab02 commit 190f532
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56 changes: 40 additions & 16 deletions git-rebase.sh
View file
Expand Up @@ -3,7 +3,7 @@
# Copyright (c) 2005 Junio C Hamano. # Copyright (c) 2005 Junio C Hamano.
# #


USAGE='[--interactive | -i] [-v] [--onto <newbase>] <upstream> [<branch>]' USAGE='[--interactive | -i] [-v] [--onto <newbase>] [<upstream>|--root] [<branch>]'
LONG_USAGE='git-rebase replaces <branch> with a new branch of the LONG_USAGE='git-rebase replaces <branch> with a new branch of the
same name. When the --onto option is provided the new branch starts same name. When the --onto option is provided the new branch starts
out with a HEAD equal to <newbase>, otherwise it is equal to <upstream> out with a HEAD equal to <newbase>, otherwise it is equal to <upstream>
Expand Down Expand Up @@ -47,6 +47,7 @@ dotest="$GIT_DIR"/rebase-merge
prec=4 prec=4
verbose= verbose=
git_am_opt= git_am_opt=
rebase_root=


continue_merge () { continue_merge () {
test -n "$prev_head" || die "prev_head must be defined" test -n "$prev_head" || die "prev_head must be defined"
Expand Down Expand Up @@ -297,6 +298,9 @@ do
-C*) -C*)
git_am_opt="$git_am_opt $1" git_am_opt="$git_am_opt $1"
;; ;;
--root)
rebase_root=t
;;
-*) -*)
usage usage
;; ;;
Expand Down Expand Up @@ -344,34 +348,46 @@ case "$diff" in
;; ;;
esac esac


# The upstream head must be given. Make sure it is valid. if test -z "$rebase_root"
upstream_name="$1" then
upstream=`git rev-parse --verify "${upstream_name}^0"` || # The upstream head must be given. Make sure it is valid.
die "invalid upstream $upstream_name" upstream_name="$1"
shift
upstream=`git rev-parse --verify "${upstream_name}^0"` ||
die "invalid upstream $upstream_name"
unset root_flag
upstream_arg="$upstream_name"
else
test -z "$newbase" && die "--root must be used with --onto"
unset upstream_name
unset upstream
root_flag="--root"
upstream_arg="$root_flag"
fi


# Make sure the branch to rebase onto is valid. # Make sure the branch to rebase onto is valid.
onto_name=${newbase-"$upstream_name"} onto_name=${newbase-"$upstream_name"}
onto=$(git rev-parse --verify "${onto_name}^0") || exit onto=$(git rev-parse --verify "${onto_name}^0") || exit


# If a hook exists, give it a chance to interrupt # If a hook exists, give it a chance to interrupt
run_pre_rebase_hook ${1+"$@"} run_pre_rebase_hook "$upstream_arg" "$@"


# If the branch to rebase is given, that is the branch we will rebase # If the branch to rebase is given, that is the branch we will rebase
# $branch_name -- branch being rebased, or HEAD (already detached) # $branch_name -- branch being rebased, or HEAD (already detached)
# $orig_head -- commit object name of tip of the branch before rebasing # $orig_head -- commit object name of tip of the branch before rebasing
# $head_name -- refs/heads/<that-branch> or "detached HEAD" # $head_name -- refs/heads/<that-branch> or "detached HEAD"
switch_to= switch_to=
case "$#" in case "$#" in
2) 1)
# Is it "rebase other $branchname" or "rebase other $commit"? # Is it "rebase other $branchname" or "rebase other $commit"?
branch_name="$2" branch_name="$1"
switch_to="$2" switch_to="$1"


if git show-ref --verify --quiet -- "refs/heads/$2" && if git show-ref --verify --quiet -- "refs/heads/$1" &&
branch=$(git rev-parse -q --verify "refs/heads/$2") branch=$(git rev-parse -q --verify "refs/heads/$1")
then then
head_name="refs/heads/$2" head_name="refs/heads/$1"
elif branch=$(git rev-parse -q --verify "$2") elif branch=$(git rev-parse -q --verify "$1")
then then
head_name="detached HEAD" head_name="detached HEAD"
else else
Expand All @@ -393,7 +409,8 @@ case "$#" in
esac esac
orig_head=$branch orig_head=$branch


# Now we are rebasing commits $upstream..$branch on top of $onto # Now we are rebasing commits $upstream..$branch (or with --root,
# everything leading up to $branch) on top of $onto


# Check if we are already based on $onto with linear history, # Check if we are already based on $onto with linear history,
# but this should be done only when upstream and onto are the same. # but this should be done only when upstream and onto are the same.
Expand Down Expand Up @@ -429,10 +446,17 @@ then
exit 0 exit 0
fi fi


if test -n "$rebase_root"
then
revisions="$onto..$orig_head"
else
revisions="$upstream..$orig_head"
fi

if test -z "$do_merge" if test -z "$do_merge"
then then
git format-patch -k --stdout --full-index --ignore-if-in-upstream \ git format-patch -k --stdout --full-index --ignore-if-in-upstream \
"$upstream..$orig_head" | $root_flag "$revisions" |
git am $git_am_opt --rebasing --resolvemsg="$RESOLVEMSG" && git am $git_am_opt --rebasing --resolvemsg="$RESOLVEMSG" &&
move_to_original_branch move_to_original_branch
ret=$? ret=$?
Expand All @@ -455,7 +479,7 @@ echo "$orig_head" > "$dotest/orig-head"
echo "$head_name" > "$dotest/head-name" echo "$head_name" > "$dotest/head-name"


msgnum=0 msgnum=0
for cmt in `git rev-list --reverse --no-merges "$upstream..$orig_head"` for cmt in `git rev-list --reverse --no-merges "$revisions"`
do do
msgnum=$(($msgnum + 1)) msgnum=$(($msgnum + 1))
echo "$cmt" > "$dotest/cmt.$msgnum" echo "$cmt" > "$dotest/cmt.$msgnum"
Expand Down
86 changes: 86 additions & 0 deletions t/t3412-rebase-root.sh
View file
@@ -0,0 +1,86 @@
#!/bin/sh

test_description='git rebase --root
Tests if git rebase --root --onto <newparent> can rebase the root commit.
'
. ./test-lib.sh

test_expect_success 'prepare repository' '
echo 1 > A &&
git add A &&
git commit -m 1 &&
echo 2 > A &&
git add A &&
git commit -m 2 &&
git symbolic-ref HEAD refs/heads/other &&
rm .git/index &&
echo 3 > B &&
git add B &&
git commit -m 3 &&
echo 1 > A &&
git add A &&
git commit -m 1b &&
echo 4 > B &&
git add B &&
git commit -m 4
'

test_expect_success 'rebase --root expects --onto' '
test_must_fail git rebase --root
'

test_expect_success 'setup pre-rebase hook' '
mkdir -p .git/hooks &&
cat >.git/hooks/pre-rebase <<EOF &&
#!$SHELL_PATH
echo "\$1,\$2" >.git/PRE-REBASE-INPUT
EOF
chmod +x .git/hooks/pre-rebase
'
cat > expect <<EOF
4
3
2
1
EOF

test_expect_success 'rebase --root --onto <newbase>' '
git checkout -b work &&
git rebase --root --onto master &&
git log --pretty=tformat:"%s" > rebased &&
test_cmp expect rebased
'

test_expect_success 'pre-rebase got correct input (1)' '
test "z$(cat .git/PRE-REBASE-INPUT)" = z--root,
'

test_expect_success 'rebase --root --onto <newbase> <branch>' '
git branch work2 other &&
git rebase --root --onto master work2 &&
git log --pretty=tformat:"%s" > rebased2 &&
test_cmp expect rebased2
'

test_expect_success 'pre-rebase got correct input (2)' '
test "z$(cat .git/PRE-REBASE-INPUT)" = z--root,work2
'

test_expect_success 'setup pre-rebase hook that fails' '
mkdir -p .git/hooks &&
cat >.git/hooks/pre-rebase <<EOF &&
#!$SHELL_PATH
false
EOF
chmod +x .git/hooks/pre-rebase
'

test_expect_success 'pre-rebase hook stops rebase' '
git checkout -b stops1 other &&
GIT_EDITOR=: test_must_fail git rebase --root --onto master &&
test "z$(git symbolic-ref HEAD)" = zrefs/heads/stops1
test 0 = $(git rev-list other...stops1 | wc -l)
'

test_done

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