Re: [RFC] Rebasing merges: a jorney to the ultimate solution (Road Clear)

On 28/02/2018 02:33, Igor Djordjevic wrote:

In case anyone has a wish to examine my (now pretty messy) test script, here it is - sorry for not having time to clean it up! :(

What I get when I diff original and "rebased" merge is this:

    diff --git a/test.txt b/test.txt
    index a82470b..d458032 100644
    --- a/test.txt
    +++ b/test.txt
    @@ -1,10 +1,14 @@
    +A21
    +A22
    +A23
    +A24
    +A25
     A1
     A2
    -B11
    +B1111
     A3
     A4
     A5
    -B12
     A6
     A7
     A8
    @@ -14,6 +18,7 @@ A10
     A11
     A12
     A13
    +BX
     A14
     B2
     A15

... where A21 to A25 are additions due to new base, B11 was interactively amended to B1111, B12 was interactively dropped, and BX interactively added :)

We don`t see line X here, being an "evil merge" amendment being correctly preserved from original merge commit (thus not a difference). If we do `git show` of the "rebased" merge, we get this, as expected:

    diff --cc test.txt
    index b173cef,fad39a8..d458032
    --- a/test.txt
    +++ b/test.txt
    @@@ -13,6 -13,6 +13,7 @@@ A
      A7
      A8
      A9
    ++X
      A10
      A11
      A12

Regards, Buga

-- 8< -- #!/bin/sh

# rm -rf ./.git # rm -f ./test.txt

git init

touch ./test.txt git add -- test.txt

for i in {1..20}
do
	echo A$i >>test.txt
	git commit -am "A$i"
done

git checkout -b b1 sed -i '3iB11' test.txt git commit -am "B11" sed -i '7iB12' test.txt git commit -am "B12"

git checkout -b b2 HEAD^ sed -i '16iB2' test.txt git commit -am "B2"

git checkout -b merge b1 git merge --no-commit b2 sed -i '12iX' test.txt # amend merge commit git commit -am "M" git tag original-merge

git checkout master
for i in {1..5}
do
	j=`expr "$i" + 20`
	sed -i "${i}iA${j}" test.txt
	git commit -am "A$j"
done

# simple/naive demonstration of proposed merge rebasing logic # using described "Trivial Merge" (TM, or "Angel Merge"), # preserving merge commit manual amendments, but still respecting # interactively rebased added/modified/dropped commits :)

# read -p "Press enter to continue" git checkout b1 git cherry-pick -m1 original-merge && git tag U1 git reset --hard HEAD^^ # drop U1 and last b1 commit sed -i '/B11/c\B1111' test.txt git commit -a --amend --no-edit git rebase master git cherry-pick U1 && git tag U1-prime

# read -p "Press enter to continue" git checkout b2 git cherry-pick -m2 original-merge && git tag U2 git reset --hard HEAD^ # drop U2 git rebase master sed -i '20iBX' test.txt git commit -am "BX" # add new commit git cherry-pick U2 && git tag U2-prime

git diff U1 U1-prime | git apply --3way && git commit -m "U2-second" && git tag U2-second git checkout b1 git diff U2 U2-prime | git apply --3way && git commit -m "U1-second" && git tag U1-second

# read -p "Press enter to continue" git branch -f merge b1 git checkout merge git merge b2 --no-commit git commit -a --reuse-message original-merge git tag angel-merge

# read -p "Press enter to continue" git reset --hard b1^ git read-tree --reset angel-merge git update-ref refs/heads/merge "$(git show -s --format=%B original-merge | git commit-tree "$(git write-tree)" -p "$(git rev-parse b1^^)" -p "$(git rev-parse b2^^)")" git tag -f angel-merge git checkout angel-merge . git branch -f b1 b1^^ git branch -f b2 b2^^

# show resulting graph echo git log --all --decorate --oneline --graph

# comparison between original merge and rebased merge, # showing merge commit amendment "X" being preserved during rebase # (not shown in diff) echo echo 'diff original-merge angel-merge:' git diff original-merge angel-merge