Package com.google.gerrit.server.patch

Class GitPositionTransformer

java.lang.Object

com.google.gerrit.server.patch.GitPositionTransformer

public class GitPositionTransformer
extends Object

Transformer of GitPositionTransformer.Positions in one Git tree to GitPositionTransformer.Positions in another Git tree given the GitPositionTransformer.Mappings between the trees.

The base idea is that a GitPositionTransformer.Position in the source tree can be translated/mapped to a corresponding GitPositionTransformer.Position in the target tree when we know how the target tree changed compared to the source tree. As long as GitPositionTransformer.Positions are only defined via file path and line range, we only need to know which file path in the source tree corresponds to which file path in the target tree and how the lines within that file changed from the source to the target tree.

The algorithm is roughly:

1. Go over all positions and replace the file path for each of them with the corresponding one in the target tree. If a file path maps to two file paths in the target tree (copied file), duplicate the position entry and use each of the new file paths with it. If a file path maps to no file in the target tree (deleted file), apply the specified conflict strategy (e.g. drop position completely or map to next best guess).
2. Per file path, go through the file from top to bottom and keep track of how the range mappings for that file shift the lines. Derive the shifted amount by comparing the number of lines between source and target in the range mapping. While going through the file, shift each encountered position by the currently tracked amount. If a position overlaps with the lines of a range mapping, apply the specified conflict strategy (e.g. drop position completely or map to next best guess).

Nested Class Summary

Nested Classes

Modifier and Type	Class	Description
static class	GitPositionTransformer.BestPositionOnConflict	A strategy which tries to select the next suitable GitPositionTransformer.Position on a conflicting mapping.
static class	GitPositionTransformer.FileMapping	A mapping of attributes from a file in one Git tree (source) to a file in another Git tree (target).
static class	GitPositionTransformer.Mapping	A mapping from a GitPositionTransformer.Position in one Git commit/tree (source) to a GitPositionTransformer.Position in another Git commit/tree (target).
static class	GitPositionTransformer.OmitPositionOnConflict	A strategy which drops any GitPositionTransformer.Positions on a conflicting mapping.
static class	GitPositionTransformer.Position	A position within the tree of a Git commit.
static interface	GitPositionTransformer.PositionConflictStrategy	Strategy indicating how to handle GitPositionTransformer.Positions for which mapping conflicts exist.
static class	GitPositionTransformer.PositionedEntity<T>	Wrapper around an instance of T which annotates it with a GitPositionTransformer.Position.
static class	GitPositionTransformer.Range	A range.
static class	GitPositionTransformer.RangeMapping	A mapping of a line range in one Git tree (source) to the corresponding line range in another Git tree (target).

Constructor Summary

Constructors

Constructor	Description
GitPositionTransformer(GitPositionTransformer.PositionConflictStrategy positionConflictStrategy)	Creates a new GitPositionTransformer which uses the specified strategy for conflicts.

Method Summary

Modifier and Type	Method	Description
<T> com.google.common.collect.ImmutableList<GitPositionTransformer.PositionedEntity<T>>	transform(Collection<GitPositionTransformer.PositionedEntity<T>> entities, Set<GitPositionTransformer.Mapping> mappings)	Transforms the GitPositionTransformer.Positions of the specified entities as indicated via the GitPositionTransformer.Mappings.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

GitPositionTransformer

public GitPositionTransformer(GitPositionTransformer.PositionConflictStrategy positionConflictStrategy)

Creates a new GitPositionTransformer which uses the specified strategy for conflicts.

Method Detail

transform

public <T> com.google.common.collect.ImmutableList<GitPositionTransformer.PositionedEntity<T>> transform(Collection<GitPositionTransformer.PositionedEntity<T>> entities,
                                                                                                         Set<GitPositionTransformer.Mapping> mappings)

Transforms the GitPositionTransformer.Positions of the specified entities as indicated via the GitPositionTransformer.Mappings.

This is typically used to transform the GitPositionTransformer.Positions in one Git tree (source) to the corresponding GitPositionTransformer.Positions in another Git tree (target). The GitPositionTransformer.Mappings need to indicate all relevant changes between the source and target tree. GitPositionTransformer.Mappings for files not referenced by the given GitPositionTransformer.Positions need not be specified. They can be included, though, as they aren't harmful.

Type Parameters:

T - an entity which has a GitPositionTransformer.Position

Parameters:

entities - the entities whose GitPositionTransformer.Position should be mapped to the target tree

mappings - the mappings describing all relevant changes between the source and the target tree

Returns:

a list of entities with transformed positions. There are no guarantees about the order of the returned elements.