Re: [PATCH] transplant: move a series of commits to a different parent

Steffen Prohaska, Sun, Jun 24, 2007 11:05:29 +0200:

quoted

Steffen Prohaska, Sat, Jun 23, 2007 21:27:57 +0200:

quoted

+for commit in $(git-rev-list --reverse $from..$to)
+do
+    echo "rewriting commit $commit..."
+    git-diff-tree -r $commit | grep ^: | cut -b 9-15,57-97,100- |
+    while read mode sha path
+    do
+        echo " $mode $sha $path"
+        git-update-index --add --cacheinfo $mode $sha $path
+    done

Why not just read-tree for every commit? It is not like you're
modifying the repository in any way, just changing parenthood. That'd
solve the problem with deletions.
So it should be enough to read-tree the repo state for each and every
source commit into the index (and you can just use a temporary index
file for that, see GIT_INDEX_FILE). Than just commit the index.

I am changing the repository.

No, you don't.

I only modify the index for files that have changes in $commit. Their
content gets replaced by the content from the commit. I'm leaving
all other files untouched.

No, you don't modify anything. Ever tried to run git-status after your
script finished? Tried to understand what the output means?

This creates a new series of commits that starts from the repository
state of <onto> and has mixed in files only if they are changed in
the series of commits from..to. These files are just replaced. I'm not
trying to merge changes but just replace the whole file.

Opposed to that, read-tree would modify the content of _all_ files.

No, it wouldn't (unless you run git-read-tree -u, and I fail to see
why would you want that). You probably confuse git-read-tree with
git-checkout-index.

This is exactly what I want to achieve. The content of the files on
branch 3 is correct for all files that were committed after 2. But
because 2 is the wrong branching point all the content originating
from commits between 1 and 2 is wrong. Files committed between
2 and 3 have the right content but the branch needs to be attached
at 1.

This misses merges (see git-rev-list --parents), but does the job for
linear history:

    export GIT_INDEX_FILE="$(git rev-parse --git-dir)/tr.idx"
    parent=$(git rev-parse "$onto")
    git rev-list --reverse "$from..$to" | while read c
    do
	rm -f "$GIT_INDEX_FILE"
	git read-tree $c || break;
	# Authorship information here
	parent=$(git cat-file commit $c | \
	    sed -e '1,/^$/d' | \
	    git commit-tree $(git write-tree) -p "$parent")
	echo "Commit $parent"
    done