Change-Id: I224190bbb41c7cbea38388d0148ecc6dc68f3a14
Signed-off-by: Kevin Sawicki <kevin@github.com>

Additionally, defined the NoteMap.getNote method which returns a Note
instance.  These changes were necessary to enable implementation of
the NoteMerger interface (the merge method needs to instantiate a
Note) and to enable direct use of NoteMerger which expects instances
of Note class as its paramters.  Implementing creation of code review
summary notes in Gerrit [1] will make use of both of these features.

[1] https://review.source.android.com/#change,20045

Change-Id: I627aefcedcd3434deecd63fa1d3e90e303b385ac
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>

Merging Git notes branches has several differences from merging "normal"
branches. Although Git notes are initially stored as one flat tree the
tree may fanout when the number of notes becomes too large for efficient
access. In this case the first two hex digits of the note name will be
used as a subdirectory name and the rest 38 hex digits as the file name
under that directory. Similarly, when number of notes decreases a fanout
tree may collapse back into a flat tree. The Git notes merge algorithm
must take into account possibly different tree structures in different
note branches and must properly match them against each other.

Any conflict on a Git note is, by default, resolved by concatenating
the two conflicting versions of the note. A delete-edit conflict is, by
default, resolved by keeping the edit version.

The note merge logic is pluggable and the caller may provide custom
note merger that will perform different merging strategy.

Additionally, it is possible to have non-note entries inside a notes
tree. The merge algorithm must also take this fact into account and
will try to merge such non-note entries. However, in case of any merge
conflicts the merge operation will fail. Git notes merge algorithm is
currently not trying to do content merge of non-note entries.

Thanks to Shawn Pearce for patiently answering my questions related to
this topic, giving hints and providing code snippets.

Change-Id: I3b2335c76c766fd7ea25752e54087f9b19d69c88
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

We will need to iterate over all notes of a NoteMap, at least this will be
needed for testing purposes. This change also implied making the Note class
public.

Change-Id: I9b0639f9843f457ee9de43504b2499a673cd0e77
Signed-off-by: Sasa Zivkov <sasa.zivkov@sap.com>

Eclipse has some problem re-running single JUnit tests if
the tests are in Junit 3 format, but the JUnit 4 launcher
is used. This was quite unnecessary and the move was not
completed. We still have no JUnit4 test.

This completes the extermination of JUnit3. Most of the
work was global searce/replace using regular expression,
followed by numerous invocarions of quick-fix and organize
imports and verification that we had the same number of
tests before and after.

- Annotations were introduced.
- All references to JUnit3 classes removed
- Half-good replacement for getting the test name. This was
  needed to make the TestRngs work. The initialization of
  TestRngs was also made lazily since we can not longer find
  out the test name in runtime in the @Before methods.
- Renamed test classes to end with Test, with the exception
  of TestTranslateBundle, which fails from Maven
- Moved JGitTestUtil to the junit support bundle

Change-Id: Iddcd3da6ca927a7be773a9c63ebf8bb2147e2d13
Signed-off-by: Robin Rosenberg <robin.rosenberg@dewire.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

Leaf level notes trees are split into a new fan-out tree if an
insertion occurs and the tree already contains >= 256 notes in it.

The splitting may occur multiple times if all of the notes have the
same prefix; in the worst case this produces a tree path such as
"00/00/00/00/00/00/00/00/00/00/00/00/00/00/00/00/00/00/00/be" if all
of the notes begin with zeros.

Change-Id: I2d7d98f35108def9ec49936ddbdc34b13822a3c7
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

This is necessary to allow applications to wrap the note tree in
a commit and update the note branch with the new state.

Change-Id: Idbd7ead4a1b16ae2b64a30a4a01a29cfed548cdf
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

NoteMap now supports editing in-memory, allowing applications to
modify the NoteMap once it has been loaded from the branch.  The
ability to write the branch back to tree objects is not yet done,
so the edits are strictly transient.

Change-Id: I63448954abfca2a8e3e95369cd84c0d1176cdb79
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>

The NoteMap makes it easy to read a small notes tree as created by
the `git notes` command in C Git.  To make the initial implementation
simple a notes tree is read recursively into a map in memory.
This is reasonable if the application will need to access all notes,
or if there are less than 256 notes in the tree, but doesn't behave
well when the number of notes exceeds 256 and the application
doesn't need to access all of them.

We can later add support for lazily loading different subpaths,
thus fixing the large note tree problem described above.

Currently the implementation only supports reading.  Writing notes
is more complex because trees need to be expanded or collapsed at
the exact 256 entry cut-off in order to retain the same tree SHA-1
that C Git would use for the same content.  It also needs to retain
non-note tree entries such as ".gitignore" or ".gitattribute" files
that might randomly appear within a notes tree.  We can also add
writing support later.

Change-Id: I93704bd84ebf650d51de34da3f1577ef0f7a9144
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Chris Aniszczyk <caniszczyk@gmail.com>