[vcs] IDEA-117448 Don't read & store patch text until really needed

ShelvedChangeList doesn't need patch text itself to provide the changes,
this texts are loaded and parsed in ShelvedChange#getChanges when needed

=> let read patch files in "ignore content" mode & use this mode
when ShelveChangeLists are loaded.

platform/vcs-api/src/com/intellij/openapi/diff/impl/patch/PatchReader.java

@@ -52,9 +52,13 @@ public class PatchReader {
   @NonNls private static final Pattern ourContextAfterHunkStartPattern = Pattern.compile("--- (\\d+),(\\d+) ----");
 
   public PatchReader(CharSequence patchContent) {
+    this(patchContent, false);
+  }
+
+  public PatchReader(CharSequence patchContent, boolean parseHunks) {
     myLines = LineTokenizer.tokenizeIntoList(patchContent, false);
-    myAdditionalInfoParser = new AdditionalInfoParser();
-    myPatchContentParser = new PatchContentParser();
+    myAdditionalInfoParser = new AdditionalInfoParser(!parseHunks);
+    myPatchContentParser = new PatchContentParser(parseHunks);
   }
 
   public List<TextFilePatch> readAllPatches() throws PatchSyntaxException {
@@ -169,10 +173,12 @@ public class PatchReader {
   private static class AdditionalInfoParser implements Parser {
     // first is path!
     private final Map<String,Map<String, CharSequence>> myResultMap;
+    private final boolean myIgnoreMode;
     private Map<String, CharSequence> myAddMap;
     private PatchSyntaxException mySyntaxException;
 
-    private AdditionalInfoParser() {
+    private AdditionalInfoParser(boolean ignore) {
+      myIgnoreMode = ignore;
       myAddMap = new HashMap<String, CharSequence>();
       myResultMap = new HashMap<String, Map<String, CharSequence>>();
     }
@@ -194,12 +200,16 @@ public class PatchReader {
 
     @Override
     public boolean testIsStart(String start) {
-      if (mySyntaxException != null) return false;  // stop on first error
+      if (myIgnoreMode || mySyntaxException != null) return false;  // stop on first error
       return start != null && start.contains(UnifiedDiffWriter.ADDITIONAL_PREFIX);
     }
 
     @Override
     public void parse(String start, ListIterator<String> iterator) {
+      if (myIgnoreMode) {
+        return;
+      }
+
       if (! iterator.hasNext()) {
         mySyntaxException =  new PatchSyntaxException(iterator.previousIndex(), "Empty additional info header");
         return;
@@ -244,13 +254,15 @@ public class PatchReader {
 
 
   private static class PatchContentParser implements Parser {
+    private final boolean myParseHunks;
     private DiffFormat myDiffFormat = null;
     private final List<TextFilePatch> myPatches;
 
     private boolean myDiffCommandLike;
     private boolean myIndexLike;
 
-    private PatchContentParser() {
+    private PatchContentParser(boolean parseHunks) {
+      myParseHunks = parseHunks;
       myPatches = new SmartList<TextFilePatch>();
     }
 
@@ -302,7 +314,7 @@ public class PatchReader {
       }
       extractFileName(curLine, curPatch, false, myDiffCommandLike && myIndexLike);
 
-      while (iterator.hasNext()) {
+      while (myParseHunks && iterator.hasNext()) {
         PatchHunk hunk;
         if (myDiffFormat == DiffFormat.UNIFIED) {
           hunk = readNextHunkUnified(iterator);

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/shelf/ShelveChangesManager.java

@@ -665,10 +665,26 @@ public class ShelveChangesManager extends AbstractProjectComponent implements JD
     notifyStateChanged();
   }
 
-  // todo problem: control usage
-  public static List<TextFilePatch> loadPatches(Project project, final String patchPath, CommitContext commitContext) throws IOException, PatchSyntaxException {
+  @NotNull
+  public static List<TextFilePatch> loadPatches(Project project,
+                                                final String patchPath,
+                                                CommitContext commitContext) throws IOException, PatchSyntaxException {
+    return loadPatches(project, patchPath, commitContext, true);
+  }
+
+  @NotNull
+  static List<? extends FilePatch> loadPatchesWithoutContent(Project project,
+                                                             final String patchPath,
+                                                             CommitContext commitContext) throws IOException, PatchSyntaxException {
+    return loadPatches(project, patchPath, commitContext, false);
+  }
+
+  private static List<TextFilePatch> loadPatches(Project project,
+                                                 final String patchPath,
+                                                 CommitContext commitContext,
+                                                 boolean loadContent) throws IOException, PatchSyntaxException {
     char[] text = FileUtil.loadFileText(new File(patchPath), CharsetToolkit.UTF8);
-    PatchReader reader = new PatchReader(new CharArrayCharSequence(text));
+    PatchReader reader = new PatchReader(new CharArrayCharSequence(text), loadContent);
     final List<TextFilePatch> textFilePatches = reader.readAllPatches();
     final TransparentlyFailedValueI<Map<String, Map<String, CharSequence>>, PatchSyntaxException> additionalInfo = reader.getAdditionalInfo(
       null);

platform/vcs-impl/src/com/intellij/openapi/vcs/changes/shelf/ShelvedChangeList.java

@@ -24,7 +24,6 @@ package com.intellij.openapi.vcs.changes.shelf;
 
 import com.intellij.openapi.diagnostic.Logger;
 import com.intellij.openapi.diff.impl.patch.FilePatch;
-import com.intellij.openapi.diff.impl.patch.TextFilePatch;
 import com.intellij.openapi.project.Project;
 import com.intellij.openapi.util.DefaultJDOMExternalizer;
 import com.intellij.openapi.util.InvalidDataException;
@@ -109,7 +108,7 @@ public class ShelvedChangeList implements JDOMExternalizable {
   public List<ShelvedChange> getChanges(Project project) {
     if (myChanges == null) {
       try {
-        final List<TextFilePatch> list = ShelveChangesManager.loadPatches(project, PATH, null);
+        final List<? extends FilePatch> list = ShelveChangesManager.loadPatchesWithoutContent(project, PATH, null);
         myChanges = new ArrayList<ShelvedChange>();
         for (FilePatch patch : list) {
           FileStatus status;