How to add a parent commit before all other commits in Git

git

I am in a situation where I am trying to convert an open source project to Git, and I have recently gained access to historical data for the project. I have already made modifications to the repo, though, so I want to add these early changes as git commits to the beginning of the tree of commits in Git. (Yes, I am aware that this will change the SHAs for later commits; this is acceptable.) The data is provided as successive snapshots of the working directory. I want to set it up so that the state of the working directory for the later commits is not affected (I don't want to merge the changes in).

For example, if initial commit B adds files a and b to the working directory, and my historical commit A adds file a, I want to make a new commit B' parented from A that adds file b only. In both B and B', the working directory looks the same, and any subsequent commits on top of B can be safely rebased onto B'.

Is it possible to do this in Git? If so, how?

Edit: Note that I need to modify the initial commit. The standard usage of git commit appends a new commit as a child of the HEAD commit, and so does not work for the initial commit, which has no parent.

Best Answer

Something like this should work.

# Create a new branch with the old history
$ git checkout --orphan old-history    
$ git add <old-files>
$ git commit

# Rebase master on top of the branch with old-history
$ git checkout master
$ git pull --rebase . old-history

Related Solutions

Git rewrite commit parent

Let's assume this as the situation:

        A---B (topic1)
       /
...---P---C---D (topic2)

If your current branch is 'topic1', you can move commits A and B into topic2 branch by issuing git rebase topic2 topic1(or just git rebase topic2). Then the repo graph would look like

                A'--B' (topic1)
               /
...---P---C---D (topic2)

where commit D is what you considered as P'. Note, that the new parent commit needn't to be changed.

Or, more generally, if you need to move some commit(s) as descendant(s) of any commit (not necessarily the head of branch), you can use --onto parameter:

         A---B (topic1)
        /
...Q---P---C---D (topic2)

git rebase --onto topic2~3 topic1~2 topic1 or git rebase --onto Q P topic1 where Q and P are commits' SHA1s.

     A'--B' (topic1)
    /
...Q---P---C---D (topic2)

If these weren't what you intended, care to explain your situation a bit more?

How to create a cron job that will commit the project changes to git on a weekly basis

0 20 * * 0 /path_to_script

That will run the command specified (replace /path_to_script') at 20:00 local time every Sunday. The syntax for cron jobs is fairly simple, and there's a slick tool that will help you create them without remembering the code positions.

In this case, the command should be a script that runs the commit for you. I think it would be easiest in your case to write a quick shell script to change to the clone directory and then run the commit. Create a file at ~/commit.sh and put this in it (replacing /location/of/clone, of course)


#!/bin/sh
cd /location/of/clone
git-commit -m "commit message, to avoid being prompted interactively"

Then chmod +x ~/commit.sh to make it executable, and have the cron job run that (referring to it by it's full path, rather than using ~).

Best Answer

Related Solutions

Git rewrite commit parent

How to create a cron job that will commit the project changes to git on a weekly basis

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