gracey gracey - 3 months ago 14
Java Question

Using the JGIT, how can I retrieve the line numbers of added/deleted lines

Assuming the following piece of code is committed to a Git repository:

int test(){
int a = 3;
int b = 4;
int c = a + b;
return c;
}


and is later updated to

int test(){
return 7;
}


I currently have a method which uses the JGit API in order to access the Git repository where the above are committed and outputs a string which is similar to the following:

int test(){
-int a = 3;
-int b = 4;
-int c = a + b;
-return c;
+return 7;
}


Now, my requirements have changed and would like to know the line numbers of the changed lines only. So I would want something like the following:

2 -int a = 3;
3 -int b = 4;
4 -int c = a + b;
5 -return c;
2 +return 7;


Basically, the same information that the GitHub application gives when an update is made.

Any help would be greatly appreciated :)

snippet of how the -/+ lines are computed:

String oldHash = "ee3e216ab5047748a22e9ec5ad3e92834704f0cc";
Git git = null;
try {
//the path where the repo is.
git = Git.open(new File("C:\\Users\\Administrator\\Documents\\GitHub\\Trial"));
} catch (IOException e1) {
e1.printStackTrace();
}
Repository repository = git.getRepository();
ObjectId old = null;
ObjectId head = null;
//a new reader to read objects from getObjectDatabase()
ObjectReader reader = repository.newObjectReader();
//Create a new parser.
CanonicalTreeParser oldTreeIter = new CanonicalTreeParser();
CanonicalTreeParser newTreeIter = new CanonicalTreeParser();
List<DiffEntry> diffs = null;

try {
//parse a git repository string and return an ObjectId
old = repository.resolve(oldHash + "^{tree}");
head = repository.resolve("HEAD^{tree}");
//Reset this parser to walk through the given tree
oldTreeIter.reset(reader, old);
newTreeIter.reset(reader, head);
diffs = git.diff()//Returns a command object to execute a diff command
.setNewTree(newTreeIter)
.setOldTree(oldTreeIter)
.call();//returns a DiffEntry for each path which is different

} catch (RevisionSyntaxException | IOException | GitAPIException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

//DiffLineCountFilter d = new DiffLineCountFilter();
//out is the stream the formatter will write to
ByteArrayOutputStream out = new ByteArrayOutputStream();
//Create a new formatter with a default level of context.
DiffFormatter df = new DiffFormatter(out);
//Set the repository the formatter can load object contents from.
df.setRepository(git.getRepository());
ArrayList<String> diffText = new ArrayList<String>();
//A DiffEntry is 'A value class representing a change to a file' therefore for each file you have a diff entry
for(DiffEntry diff : diffs)
{
try {
//Format a patch script for one file entry.
df.format(diff);
RawText r = new RawText(out.toByteArray());
r.getLineDelimiter();


diffText.add(out.toString());
out.reset();
} catch (IOException e) {
e.printStackTrace();
}

}

Answer

Just a tip for anyone who might have this problem. I did not manage to get the line numbers of the added and deleted lines but I did manage to get a string which contains only the added and deleted lines without the other lines which were not changed.

This was simply done by adding the line:

   df.setContext(0);

in the snippet I provided above right before the line

   df.format(diff);