Implement ours/theirs content conflict resolution

Git has different conflict resolution strategies:

* There is a tree merge strategy "ours" which just ignores any changes
  from theirs ("-s ours"). JGit also has the mirror strategy "theirs"
  ignoring any changes from "ours". (This doesn't exist in C git.)
  Adapt StashApplyCommand and CherrypickCommand to be able to use those
  tree merge strategies.
* For the resolve/recursive tree merge strategies, there are content
  conflict resolution strategies "ours" and "theirs", which resolve
  any conflict hunks by taking the "ours" or "theirs" hunk. In C git
  those correspond to "-Xours" or -Xtheirs". Implement that in
  MergeAlgorithm, and add API to set and pass through such a strategy
  for resolving content conflicts.
* The "ours/theirs" content conflict resolution strategies also apply
  for binary files. Handle these cases in ResolveMerger.

Note that the content conflict resolution strategies ("-X ours/theirs")
do _not_ apply to modify/delete or delete/modify conflicts. Such
conflicts are always reported as conflicts by C git. They do apply,
however, if one side completely clears a file's content.

Bug: 501111
Change-Id: I2c9c170c61c440a2ab9c387991e7a0c3ab960e07
Signed-off-by: Thomas Wolf <thomas.wolf@paranor.ch>
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

3 files changed, 24 insertions, 2 deletions

diff --git a/org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/internal/CLIText.properties b/org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/internal/CLIText.properties
index 83846ee8e9..38deab99a0 100644
--- a/org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/internal/CLIText.properties
+++ b/org.eclipse.jgit.pgm/resources/org/eclipse/jgit/pgm/internal/CLIText.properties
@@ -115,6 +115,7 @@ metaVar_configFile=FILE
 metaVar_connProp=conn.prop
 metaVar_diffAlg=ALGORITHM
 metaVar_directory=DIRECTORY
+metaVar_extraArgument=ours|theirs
 metaVar_file=FILE
 metaVar_filepattern=filepattern
 metaVar_gitDir=GIT_DIR
@@ -217,6 +218,7 @@ timeInMilliSeconds={0} ms
 treeIsRequired=argument tree is required
 tooManyRefsGiven=Too many refs given
 unknownIoErrorStdout=An unknown I/O error occurred on standard output
+unknownExtraArgument=unknown extra argument -X {0} specified
 unknownMergeStrategy=unknown merge strategy {0} specified
 unknownSubcommand=Unknown subcommand: {0}
 unmergedPaths=Unmerged paths:
@@ -226,6 +228,7 @@ updating=Updating {0}..{1}
 usage_Aggressive=This option will cause gc to more aggressively optimize the repository at the expense of taking much more time
 usage_AlwaysFallback=Show uniquely abbreviated commit object as fallback
 usage_bareClone=Make a bare Git repository. That is, instead of creating [DIRECTORY] and placing the administrative files in [DIRECTORY]/.git, make the [DIRECTORY] itself the $GIT_DIR.
+usage_extraArgument=Pass an extra argument to a merge driver. Currently supported are "-X ours" and "-X theirs".
 usage_mirrorClone=Set up a mirror of the source repository. This implies --bare. Compared to --bare, --mirror not only maps \
 local branches of the source to local branches of the target, it maps all refs (including remote-tracking branches, notes etc.) \
 and sets up a refspec configuration such that all these refs are overwritten by a git remote update in the target repository.
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Merge.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Merge.java
index fdc449e063..ca4877fb34 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Merge.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/Merge.java
@@ -24,6 +24,7 @@ import org.eclipse.jgit.lib.AnyObjectId;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
+import org.eclipse.jgit.merge.ContentMergeStrategy;
 import org.eclipse.jgit.merge.MergeStrategy;
 import org.eclipse.jgit.merge.ResolveMerger.MergeFailureReason;
 import org.eclipse.jgit.pgm.internal.CLIText;
@@ -69,6 +70,20 @@ class Merge extends TextBuiltin {
 	@Option(name = "-m", usage = "usage_message")
 	private String message;
 
+	private ContentMergeStrategy contentStrategy = null;
+
+	@Option(name = "--strategy-option", aliases = { "-X" },
+			metaVar = "metaVar_extraArgument", usage = "usage_extraArgument")
+	void extraArg(String name) {
+		if (ContentMergeStrategy.OURS.name().equalsIgnoreCase(name)) {
+			contentStrategy = ContentMergeStrategy.OURS;
+		} else if (ContentMergeStrategy.THEIRS.name().equalsIgnoreCase(name)) {
+			contentStrategy = ContentMergeStrategy.THEIRS;
+		} else {
+			throw die(MessageFormat.format(CLIText.get().unknownExtraArgument, name));
+		}
+	}
+
 	/** {@inheritDoc} */
 	@Override
 	protected void run() {
@@ -96,8 +111,11 @@ class Merge extends TextBuiltin {
 			Ref oldHead = getOldHead();
 			MergeResult result;
 			try (Git git = new Git(db)) {
-				MergeCommand mergeCmd = git.merge().setStrategy(mergeStrategy)
-						.setSquash(squash).setFastForward(ff)
+				MergeCommand mergeCmd = git.merge()
+						.setStrategy(mergeStrategy)
+						.setContentMergeStrategy(contentStrategy)
+						.setSquash(squash)
+						.setFastForward(ff)
 						.setCommit(!noCommit);
 				if (srcRef != null) {
 					mergeCmd.include(srcRef);
diff --git a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/internal/CLIText.java b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/internal/CLIText.java
index 991b3ba58a..8e49a76a33 100644
--- a/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/internal/CLIText.java
+++ b/org.eclipse.jgit.pgm/src/org/eclipse/jgit/pgm/internal/CLIText.java
@@ -284,6 +284,7 @@ public class CLIText extends TranslationBundle {
 	/***/ public String tooManyRefsGiven;
 	/***/ public String treeIsRequired;
 	/***/ public char[] unknownIoErrorStdout;
+	/***/ public String unknownExtraArgument;
 	/***/ public String unknownMergeStrategy;
 	/***/ public String unknownSubcommand;
 	/***/ public String unmergedPaths;