Make git-merge and helpers Builtins

Hi,
   I have used Git for one year, and I join into this list for 3 or 4 
monthes. Sometime, I post some questions here and followed some 
disscusions. I have noticed that, there is a potential project in this 
GSoC "make git-merge and helplers builtins". I think I am one of the 
suitable students for this project because I am familiar with shell 
script programming and c language. And I post this message here to hope 
I can discuss more with the community about this project. 
    I have git clone the Git's source code for some days. And with some 
insight into the code, I found that some of the merge related code is 
located in sh script:  git-merge-octopus.sh  git-merge-one-file.sh 
git-merge-resovle.sh git-merge.sh git-mergetool.sh . And others are 
located in c source code: builtin-merge-base.c builtin-merge-file.c 
builtin-merge-ours.c builtin-merge-recrusive.c and merge-file.c 
merge-tree.c merge-index.c merge-recursive.h for two simple declarations.
   And git-mergetool.sh is itself an interactive shell process, I think 
there is no need to deal with it. So, the main work for this project is 
to change the other four scripts into c format. For deatails, instead of 
call the git merge-base in the shell, we make the final corresponding c 
code to call the functions in the builtin-merge-base.c. Could you please 
tell more about the work if I miss something?
  
   Finally, I have some questions about the merge code. I found there 
are many merge related code and I can't understand them at a short time. 
So, pleaes help me if you can.

   1. git-merge-file is used to merge one file, but what are 
merge-octopus and merge-resovle?
   2. I see in builtin-merge-file.c and merge-file.c, there are both 
functions used to merge file. And finally, they both call the xdl_merge 
. Could you please tell me how differenct of these to methods? I ask 
this question because I think there are some redundant code in the git 
source. Forgive me if I am wrong, I have no hostility but want to know 
why things are like that.

Thank you!

Regards! Bo

On Thu, 20 Mar 2008, Bo Yang wrote:

I think the main interesting shell script is "git-merge.sh"; the others are helpers of various sorts.

They are different "merge strategies". When merging, you can use "-s <name>" to select a program that will be used to figure out what the result should be. Some of these strategies (ours, theirs, recursive) have been built in already. "merge-octopus" is used when you're merging more than two branches at the same time, and "merge-resolve" is the usual simple merge.

builtin-merge-file has the command-line parsing code, while merge-file is called by C code. They could probably share the code around calling xdl_merge.

We often have duplicate functions from the point of view of functionality, where one is cmd_*(int argc, const char **argv, const char *prefix) and the other has arguments particular to the function; the cmd_*() one is used by the command line dispatcher.

There's also a certain amount of redundant code that's there for historical reasons. People tend to clean it up when they find it, but we've never had enough clarity in naming that somebody who needs a function to do some particular task will necessarily find an existing function for that task if there is one.

	-Daniel
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