[SCRIPT/RFC 1/3] setup.sh

On 26/11/2017 23:35, Igor Djordjevic wrote:

To begin with, you can use provided "setup.sh"[*1*] script, putting you straight into position shown on graph (2) above, with addition of tag "A" and remote branch "origin/topicA" so you could try using these as "--onto-parent" values, too.

As seen in there, change "X" is already made and staged, so you can now just run something like:

	git-commit--onto-parent.sh --onto-parent topicA

... to see the logic in action.
 
Instead of "topicA", you may try providing tag "A", remote branch 
"origin/topicA" or even plain commit hash. It`s interesting to add 
"--amend" option into the mix, too, and see what happens. Also, you 
can try using "topicB" and see the commit fail (as it doesn`t merge 
cleanly).

All this while "test.txt" file doesn`t get modified on disk (nor would any other file) - being desired behaviour, as we didn`t actually change anything inside the working tree, but just amended history of how we got here, so recompilation isn`t needlessly triggered :)

p.s. Note these two lines near the end:

	sed -i '4iX1' test.txt  # works with simple patch apply
	sed -i '17iX2' test.txt # needs three-way file merge

You can play with it, commenting out one or the other and observing how it influences "git commit --onto-parent" in regards of the parent provided.

Regards, Buga

[*1*] "setup.sh", can clean previous setup run as well, but commented 
 out here for safety, not to unexpectedly delete something for unwary 
 user.
--- 8< ---
#!/bin/sh

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

git init

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

for i in {1..10}
do
	echo $i >>test.txt	
	git commit -am "$i"
done

echo M >>test.txt git commit -am "M"

git checkout -b topicA HEAD~2

for i in 1 2
do
	sed -i "${i}iA${i}" test.txt
	git commit -am "A$i"
done
sed -i '3iA' test.txt
git commit -am "A"
git tag A

# simulate remote branch mkdir -p ./.git/refs/remotes/origin && echo $(git rev-parse HEAD^0) >$_/topicA

git checkout -b topicB master^

sed -i '4iB1' test.txt git commit -am "B1" sed -i '5iB' test.txt git commit -am "B"

git checkout -b topicC master~2

for i in 1 2
do
	j=`expr "$i" + 5`
	sed -i "${j}iC${i}" test.txt
	git commit -am "C$i"
done
sed -i "8iC" test.txt
git commit -am "C"

git checkout -b test master git merge --no-edit topicA topicB topicC

sed -i '4iX1' test.txt # works with simple patch apply sed -i '17iX2' test.txt # needs three-way file merge git add -- test.txt

echo git log --all --decorate --oneline --graph echo git diff --cached