git: read pull.rebase config value for default update method IDEA-152689

Note that '*.rebase' configs can have the following values:
  true, interactive, preserve
  yes (not specified in man)
  false, no (both not specified in man)

plugins/git4idea/src/git4idea/config/GitVersionSpecialty.java

@@ -107,6 +107,13 @@ public enum GitVersionSpecialty {
     }
   },
 
+  KNOWS_PULL_REBASE {
+    @Override
+    public boolean existsIn(@NotNull GitVersion version) {
+      return version.isLaterOrEqual(new GitVersion(1, 7, 9, 0));
+    }
+  },
+
   /**
    * {@code --no-walk=unsorted} <br/>
    * Before this version {@code --no-walk} didn't take any parameters.

plugins/git4idea/src/git4idea/update/GitUpdater.java

@@ -28,6 +28,7 @@ import git4idea.commands.Git;
 import git4idea.commands.GitCommand;
 import git4idea.commands.GitLineHandler;
 import git4idea.config.GitConfigUtil;
+import git4idea.config.GitVersionSpecialty;
 import git4idea.config.UpdateMethod;
 import git4idea.merge.MergeChangeCollector;
 import git4idea.repo.GitRepository;
@@ -37,6 +38,8 @@ import org.jetbrains.annotations.NotNull;
 import java.util.ArrayList;
 
 import static git4idea.GitUtil.HEAD;
+import static git4idea.config.UpdateMethod.MERGE;
+import static git4idea.config.UpdateMethod.REBASE;
 
 /**
  * Updates a single repository via merge or rebase.
@@ -99,19 +102,46 @@ public abstract class GitUpdater {
 
   @NotNull
   public static UpdateMethod resolveUpdateMethod(@NotNull GitRepository repository) {
+    Project project = repository.getProject();
     GitLocalBranch branch = repository.getCurrentBranch();
-    boolean rebase = false;
     if (branch != null) {
+      String branchName = branch.getName();
       try {
-        String rebaseValue = GitConfigUtil.getValue(repository.getProject(), repository.getRoot(),
-                                                    "branch." + branch.getName() + ".rebase");
-        rebase = rebaseValue != null && rebaseValue.equalsIgnoreCase("true");
+        String rebaseValue = GitConfigUtil.getValue(project, repository.getRoot(), "branch." + branchName + ".rebase");
+        if (rebaseValue != null) {
+          if (isRebaseValue(rebaseValue)) {
+            return REBASE;
+          }
+          if (rebaseValue.equalsIgnoreCase("false") || rebaseValue.equalsIgnoreCase("no")) {
+            // explicit override of a more generic pull.rebase config value
+            return MERGE;
+          }
+          LOG.warn("Unknown value for branch." + branchName + ".rebase: " + rebaseValue);
+        }
       }
       catch (VcsException e) {
-        LOG.warn("Couldn't get git config branch." + branch.getName() + ".rebase", e);
+        LOG.warn("Couldn't get git config branch." + branchName + ".rebase");
       }
     }
-    return rebase ? UpdateMethod.REBASE : UpdateMethod.MERGE;
+
+    if (GitVersionSpecialty.KNOWS_PULL_REBASE.existsIn(GitVcs.getInstance(project).getVersion())) {
+      try {
+        String pullRebaseValue = GitConfigUtil.getValue(project, repository.getRoot(), "pull.rebase");
+        if (pullRebaseValue != null && isRebaseValue(pullRebaseValue)) return REBASE;
+      }
+      catch (VcsException e) {
+        LOG.warn("Couldn't get git config pull.rebase");
+      }
+    }
+
+    return MERGE;
+  }
+
+  private static boolean isRebaseValue(@NotNull String configValue) {
+    return configValue.equalsIgnoreCase("true") ||
+           configValue.equalsIgnoreCase("interactive") ||
+           configValue.equalsIgnoreCase("preserve") ||
+           configValue.equalsIgnoreCase("yes"); // 'yes' is not specified in the man, but actually works
   }
 
   @NotNull

plugins/git4idea/tests/git4idea/update/GitUpdateMethodTest.kt

@@ -0,0 +1,47 @@
+// Copyright 2000-2017 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license that can be found in the LICENSE file.
+package git4idea.update
+
+import git4idea.config.UpdateMethod
+import git4idea.test.GitSingleRepoTest
+
+class GitUpdateMethodTest: GitSingleRepoTest() {
+
+  fun `test merge is default if no config`() {
+    assertDefaultUpdateMethod(UpdateMethod.MERGE)
+  }
+
+  fun `test rebase is default if branch-master-rebase is set to interactive`() {
+    git("config branch.master.rebase interactive")
+    assertDefaultUpdateMethod(UpdateMethod.REBASE)
+  }
+
+  fun `test rebase is default if branch-master-rebase is set to preserve`() {
+    git("config branch.master.rebase preserve")
+    assertDefaultUpdateMethod(UpdateMethod.REBASE)
+  }
+
+  fun `test rebase is default if pull-rebase is set to true`() {
+    git("config pull.rebase true")
+    assertDefaultUpdateMethod(UpdateMethod.REBASE)
+  }
+
+  fun `test rebase is default if pull-rebase is set to interactive`() {
+    git("config pull.rebase interactive")
+    assertDefaultUpdateMethod(UpdateMethod.REBASE)
+  }
+
+  fun `test rebase is default if pull-rebase is set to preserve`() {
+    git("config pull.rebase preserve")
+    assertDefaultUpdateMethod(UpdateMethod.REBASE)
+  }
+
+  fun `test branch config overrides pull-rebase`() {
+    git("config pull.rebase true")
+    git("config branch.master.rebase false")
+    assertDefaultUpdateMethod(UpdateMethod.MERGE)
+  }
+
+  private fun assertDefaultUpdateMethod(expectedMethod: UpdateMethod) {
+    assertEquals("Default update method is incorrect", expectedMethod, GitUpdater.resolveUpdateMethod(repo))
+  }
+}