gitpython and git diff

Question

I am looking to get only the diff of a file changed from a git repo. Right now, I am using gitpython to actually get the commit objects and the files of git changes, but I want to do a dependency analysis on only the parts of the file changed. Is there any way to get the git diff from git python? Or am I going to have to compare each of the files by reading line by line?

Answer 1

If you want to access the contents of the diff, try this:

repo = git.Repo(repo_root.as_posix())
commit_dev = repo.commit("dev")
commit_origin_dev = repo.commit("origin/dev")
diff_index = commit_origin_dev.diff(commit_dev)

for diff_item in diff_index.iter_change_type('M'):
    print("A blob:\n{}".format(diff_item.a_blob.data_stream.read().decode('utf-8')))
    print("B blob:\n{}".format(diff_item.b_blob.data_stream.read().decode('utf-8'))) 

This will print the contents of each file.

Answer 2

You can use GitPython with the git command "diff", just need to use the "tree" object of each commit or the branch for that you want to see the diffs, for example:

repo = Repo('/git/repository')
t = repo.head.commit.tree
repo.git.diff(t)

This will print "all" the diffs for all files included in this commit, so if you want each one you must iterate over them.

With the actual branch it's:

repo.git.diff('HEAD~1')

Hope this help, regards.

Answer 3

Git does not store the diffs, as you have noticed. Given two blobs (before and after a change), you can use Python's difflib module to compare the data.

Answer 4

I'd suggest you to use PyDriller instead (it uses GitPython internally). Much easier to use:

for commit in Repository("path_to_repo").traverse_commits():
    for modified_file in commit.modified_files: # here you have the list of modified files
        print(modified_file.diff)
        # etc...

You can also analyze a single commit by doing:

for commit in RepositoryMining("path_to_repo", single="123213")

Answer 5

If you're looking to recreate something close to what a standard git diff would show, try:

# cloned_repo = git.Repo.clone_from(
#     url=ssh_url,
#     to_path=repo_dir,
#     env={"GIT_SSH_COMMAND": "ssh -i " + SSH_KEY},
# ) 
for diff_item in cloned_repo.index.diff(None, create_patch=True):
    repo_diff += (
        f"--- a/{diff_item.a_blob.name}\n+++ b/{diff_item.b_blob.name}\n"
        f"{diff_item.diff.decode('utf-8')}\n\n"
        )

Answer 6

If you want to do git diff on a file between two commits this is the way to do it:

import git
   
repo = git.Repo()
path_to_a_file = "diff_this_file_across_commits.txt"
   
commits_touching_path = list(repo.iter_commits(paths=path))
   
print repo.git.diff(commits_touching_path[0], commits_touching_path[1], path_to_a_file)

This will show you the differences between two latest commits that were done to the file you specify.

Answer 7

repo.git.diff("main", "head~5")

Answer 8

PyDriller +1

pip install pydriller

But with the new API:

Breaking API: ```
from pydriller import Repository

for commit in Repository('https://github.com/ishepard/pydriller').traverse_commits():
    print(commit.hash)
    print(commit.msg)
    print(commit.author.name)

    for file in commit.modified_files:
        print(file.filename, ' has changed')

Answer 9

Here is how you do it

import git
repo = git.Repo("path/of/repo/")

# the below gives us all commits
repo.commits()

# take the first and last commit

a_commit = repo.commits()[0]
b_commit = repo.commits()[1]

# now get the diff
repo.diff(a_commit,b_commit)