chore: fetch remote reference in local (#38009)

## Description
- Added fetch remote CGS Impl

Fixes #
> [!WARNING]  
> _If no issue exists, please create an issue first, and check with the
maintainers if the issue is valid._

## Automation

/ok-to-test tags="@tag.Git"

### 🔍 Cypress test results
<!-- This is an auto-generated comment: Cypress test results  -->
> [!WARNING]
> Tests have not run on the HEAD
d964d59 yet
> <hr>Mon, 09 Dec 2024 07:03:35 UTC
<!-- end of auto-generated comment: Cypress test results  -->


## Communication
Should the DevRel and Marketing teams inform users about this change?
- [ ] Yes
- [ ] No


<!-- This is an auto-generated comment: release notes by coderabbit.ai
-->
## Summary by CodeRabbit

## Release Notes

- **New Features**
- Introduced new methods for fetching remote changes in various Git
services, enhancing synchronization capabilities.
	- Added new fields for internal metadata management.
- Implemented user session management improvements for better handling
of user-related data.
- Added analytics tracking for unit execution time to improve
performance insights.

- **Bug Fixes**
	- Enhanced error handling in new fetch methods to ensure robustness.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->

app/server/appsmith-server/src/main/java/com/appsmith/server/domains/ce/GitArtifactMetadataCE.java

@@ -2,6 +2,7 @@
 
 import com.appsmith.external.models.AppsmithDomain;
 import com.appsmith.external.views.Views;
+import com.appsmith.server.constants.ce.RefType;
 import com.appsmith.server.domains.AutoCommitConfig;
 import com.appsmith.server.domains.GitAuth;
 import com.appsmith.server.domains.GitProfile;
@@ -24,6 +25,16 @@ public class GitArtifactMetadataCE implements AppsmithDomain {
     @JsonView(Views.Public.class)
     String branchName;
 
+    // TODO: make this public view and remove transient annotation once implmentation completes
+    @Transient
+    @JsonView(Views.Internal.class)
+    String refName;
+
+    // TODO: make this public view and remove transient annotation once implementation completes
+    @Transient
+    @JsonView(Views.Internal.class)
+    RefType refType;
+
     // Git default branch corresponding to the remote git repo to which the application is connected to
     @JsonView(Views.Public.class)
     String defaultBranchName;

app/server/appsmith-server/src/main/java/com/appsmith/server/git/central/CentralGitServiceCE.java

@@ -2,6 +2,7 @@
 
 import com.appsmith.git.dto.CommitDTO;
 import com.appsmith.server.constants.ArtifactType;
+import com.appsmith.server.constants.ce.RefType;
 import com.appsmith.server.domains.Artifact;
 import com.appsmith.server.dtos.ArtifactImportDTO;
 import com.appsmith.server.dtos.GitConnectDTO;
@@ -23,4 +24,11 @@ Mono<String> commitArtifact(
             CommitDTO commitDTO, String branchedArtifactId, ArtifactType artifactType, GitType gitType);
 
     Mono<? extends Artifact> detachRemote(String branchedArtifactId, ArtifactType artifactType, GitType gitType);
+
+    Mono<String> fetchRemoteChanges(
+            String referenceArtifactId,
+            boolean isFileLock,
+            ArtifactType artifactType,
+            GitType gitType,
+            RefType refType);
 }

app/server/appsmith-server/src/main/java/com/appsmith/server/git/central/CentralGitServiceCECompatibleImpl.java

@@ -10,6 +10,7 @@
 import com.appsmith.server.helpers.GitPrivateRepoHelper;
 import com.appsmith.server.imports.internal.ImportService;
 import com.appsmith.server.plugins.base.PluginService;
+import com.appsmith.server.services.SessionUserService;
 import com.appsmith.server.services.UserDataService;
 import com.appsmith.server.services.WorkspaceService;
 import com.appsmith.server.solutions.DatasourcePermission;
@@ -26,6 +27,7 @@ public CentralGitServiceCECompatibleImpl(
             GitProfileUtils gitProfileUtils,
             GitAnalyticsUtils gitAnalyticsUtils,
             UserDataService userDataService,
+            SessionUserService sessionUserService,
             GitArtifactHelperResolver gitArtifactHelperResolver,
             GitHandlingServiceResolver gitHandlingServiceResolver,
             GitPrivateRepoHelper gitPrivateRepoHelper,
@@ -41,6 +43,7 @@ public CentralGitServiceCECompatibleImpl(
                 gitProfileUtils,
                 gitAnalyticsUtils,
                 userDataService,
+                sessionUserService,
                 gitArtifactHelperResolver,
                 gitHandlingServiceResolver,
                 gitPrivateRepoHelper,

app/server/appsmith-server/src/main/java/com/appsmith/server/git/central/CentralGitServiceCEImpl.java

@@ -18,6 +18,7 @@
 import com.appsmith.server.domains.GitAuth;
 import com.appsmith.server.domains.GitProfile;
 import com.appsmith.server.domains.Plugin;
+import com.appsmith.server.domains.User;
 import com.appsmith.server.domains.UserData;
 import com.appsmith.server.domains.Workspace;
 import com.appsmith.server.dtos.ArtifactExchangeJson;
@@ -36,6 +37,7 @@
 import com.appsmith.server.imports.internal.ImportService;
 import com.appsmith.server.plugins.base.PluginService;
 import com.appsmith.server.services.GitArtifactHelper;
+import com.appsmith.server.services.SessionUserService;
 import com.appsmith.server.services.UserDataService;
 import com.appsmith.server.services.WorkspaceService;
 import com.appsmith.server.solutions.DatasourcePermission;
@@ -44,6 +46,7 @@
 import lombok.extern.slf4j.Slf4j;
 import org.eclipse.jgit.api.errors.InvalidRemoteException;
 import org.eclipse.jgit.api.errors.TransportException;
+import org.eclipse.jgit.lib.BranchTrackingStatus;
 import org.springframework.stereotype.Service;
 import org.springframework.util.CollectionUtils;
 import org.springframework.util.StringUtils;
@@ -65,6 +68,7 @@
 import static com.appsmith.external.git.constants.ce.GitConstantsCE.GIT_PROFILE_ERROR;
 import static com.appsmith.external.git.constants.ce.GitSpanCE.OPS_COMMIT;
 import static com.appsmith.external.helpers.AppsmithBeanUtils.copyNestedNonNullProperties;
+import static com.appsmith.server.constants.FieldName.BRANCH_NAME;
 import static com.appsmith.server.constants.FieldName.DEFAULT;
 import static com.appsmith.server.constants.SerialiseArtifactObjective.VERSION_CONTROL;
 import static java.lang.Boolean.FALSE;
@@ -79,6 +83,7 @@ public class CentralGitServiceCEImpl implements CentralGitServiceCE {
     private final GitProfileUtils gitProfileUtils;
     private final GitAnalyticsUtils gitAnalyticsUtils;
     private final UserDataService userDataService;
+    private final SessionUserService sessionUserService;
 
     protected final GitArtifactHelperResolver gitArtifactHelperResolver;
     protected final GitHandlingServiceResolver gitHandlingServiceResolver;
@@ -940,6 +945,108 @@ private boolean isBaseGitMetadataInvalid(GitArtifactMetadata gitArtifactMetadata
                         .isGitAuthInvalid(gitArtifactMetadata.getGitAuth());
     }
 
+    public Mono<String> fetchRemoteChanges(
+            Artifact baseArtifact, Artifact refArtifact, boolean isFileLock, GitType gitType, RefType refType) {
+
+        if (refArtifact == null
+                || baseArtifact == null
+                || isBaseGitMetadataInvalid(baseArtifact.getGitArtifactMetadata(), gitType)) {
+            return Mono.error(new AppsmithException(AppsmithError.GIT_GENERIC_ERROR));
+        }
+
+        GitArtifactMetadata baseArtifactGitData = baseArtifact.getGitArtifactMetadata();
+        GitArtifactMetadata refArtifactGitData = refArtifact.getGitArtifactMetadata();
+
+        String baseArtifactId = baseArtifactGitData.getDefaultArtifactId();
+
+        // TODO add gitType in all error messages.
+        if (refArtifactGitData == null || !hasText(refArtifactGitData.getRefName())) {
+            return Mono.error(new AppsmithException(AppsmithError.INVALID_PARAMETER, BRANCH_NAME));
+        }
+
+        Mono<User> currUserMono = sessionUserService.getCurrentUser().cache(); // will be used to send analytics event
+        Mono<Boolean> acquireGitLockMono =
+                gitRedisUtils.acquireGitLock(baseArtifactId, GitConstants.GitCommandConstants.FETCH_REMOTE, isFileLock);
+
+        ArtifactJsonTransformationDTO jsonTransformationDTO = new ArtifactJsonTransformationDTO();
+        jsonTransformationDTO.setWorkspaceId(baseArtifact.getWorkspaceId());
+        jsonTransformationDTO.setBaseArtifactId(baseArtifactGitData.getDefaultArtifactId());
+        jsonTransformationDTO.setRepoName(baseArtifactGitData.getRepoName());
+        jsonTransformationDTO.setArtifactType(baseArtifact.getArtifactType());
+        jsonTransformationDTO.setRefName(refArtifactGitData.getRefName());
+        jsonTransformationDTO.setRefType(refType);
+
+        GitHandlingService gitHandlingService = gitHandlingServiceResolver.getGitHandlingService(gitType);
+
+        // current user mono has been zipped just to run in parallel.
+        Mono<String> fetchRemoteMono = acquireGitLockMono
+                .then(Mono.defer(() ->
+                        gitHandlingService.fetchRemoteChanges(jsonTransformationDTO, baseArtifactGitData.getGitAuth())))
+                .flatMap(fetchedRemoteStatusString -> {
+                    return gitRedisUtils.releaseFileLock(baseArtifactId).thenReturn(fetchedRemoteStatusString);
+                })
+                .onErrorResume(throwable -> {
+                    /*
+                     in case of any error, the global exception handler will release the lock
+                     hence we don't need to do that manually
+                    */
+                    log.error(
+                            "Error to fetch from remote for application: {}, branch: {}, git type {}",
+                            baseArtifactId,
+                            refArtifactGitData.getRefName(),
+                            gitType,
+                            throwable);
+                    return Mono.error(
+                            new AppsmithException(AppsmithError.GIT_ACTION_FAILED, "fetch", throwable.getMessage()));
+                })
+                .elapsed()
+                .zipWith(currUserMono)
+                .flatMap(objects -> {
+                    Long elapsedTime = objects.getT1().getT1();
+                    String fetchRemote = objects.getT1().getT2();
+                    User currentUser = objects.getT2();
+                    return gitAnalyticsUtils
+                            .sendUnitExecutionTimeAnalyticsEvent(
+                                    AnalyticsEvents.GIT_FETCH.getEventName(), elapsedTime, currentUser, refArtifact)
+                            .thenReturn(fetchRemote);
+                })
+                .name(GitSpan.OPS_FETCH_REMOTE)
+                .tap(Micrometer.observation(observationRegistry));
+
+        return Mono.create(sink -> {
+            fetchRemoteMono.subscribe(sink::success, sink::error, null, sink.currentContext());
+        });
+    }
+
+    /**
+     * This method is responsible to compare the current branch with the remote branch.
+     * Comparing means finding two numbers - how many commits ahead and behind the local branch is.
+     * It'll do the following things -
+     * 1. Checkout (if required) to the branch to make sure we are comparing the right branch
+     * 2. Run a git fetch command to fetch the latest changes from the remote
+     *
+     * @param refArtifactId      id of the reference
+     * @param isFileLock         whether to add file lock or not
+     * @param artifactType
+     * @return Mono of {@link BranchTrackingStatus}
+     */
+    @Override
+    public Mono<String> fetchRemoteChanges(
+            String refArtifactId, boolean isFileLock, ArtifactType artifactType, GitType gitType, RefType refType) {
+        GitArtifactHelper<?> artifactGitHelper = gitArtifactHelperResolver.getArtifactHelper(artifactType);
+        AclPermission artifactEditPermission = artifactGitHelper.getArtifactEditPermission();
+
+        Mono<Tuple2<? extends Artifact, ? extends Artifact>> baseAndBranchedArtifactMono =
+                getBaseAndBranchedArtifacts(refArtifactId, artifactType, artifactEditPermission);
+
+        return baseAndBranchedArtifactMono.flatMap(artifactTuples -> {
+            Artifact baseArtifact = artifactTuples.getT1();
+            Artifact refArtifact = artifactTuples.getT2();
+
+            return fetchRemoteChanges(baseArtifact, refArtifact, isFileLock, gitType, refType);
+        });
+    }
+
     /**
      * Returns baseArtifact and branchedArtifact
      * This operation is quite frequently used, hence providing the right set

app/server/appsmith-server/src/main/java/com/appsmith/server/git/central/CentralGitServiceImpl.java

@@ -10,6 +10,7 @@
 import com.appsmith.server.helpers.GitPrivateRepoHelper;
 import com.appsmith.server.imports.internal.ImportService;
 import com.appsmith.server.plugins.base.PluginService;
+import com.appsmith.server.services.SessionUserService;
 import com.appsmith.server.services.UserDataService;
 import com.appsmith.server.services.WorkspaceService;
 import com.appsmith.server.solutions.DatasourcePermission;
@@ -25,6 +26,7 @@ public CentralGitServiceImpl(
             GitProfileUtils gitProfileUtils,
             GitAnalyticsUtils gitAnalyticsUtils,
             UserDataService userDataService,
+            SessionUserService sessionUserService,
             GitArtifactHelperResolver gitArtifactHelperResolver,
             GitHandlingServiceResolver gitHandlingServiceResolver,
             GitPrivateRepoHelper gitPrivateRepoHelper,
@@ -40,6 +42,7 @@ public CentralGitServiceImpl(
                 gitProfileUtils,
                 gitAnalyticsUtils,
                 userDataService,
+                sessionUserService,
                 gitArtifactHelperResolver,
                 gitHandlingServiceResolver,
                 gitPrivateRepoHelper,

app/server/appsmith-server/src/main/java/com/appsmith/server/git/central/GitHandlingServiceCE.java

@@ -56,4 +56,6 @@ Mono<Boolean> prepareChangesToBeCommitted(
 
     Mono<Tuple2<? extends Artifact, String>> commitArtifact(
             Artifact branchedArtifact, CommitDTO commitDTO, ArtifactJsonTransformationDTO jsonTransformationDTO);
+
+    Mono<String> fetchRemoteChanges(ArtifactJsonTransformationDTO jsonTransformationDTO, GitAuth gitAuth);
 }

app/server/appsmith-server/src/main/java/com/appsmith/server/git/fs/GitFSServiceCEImpl.java

@@ -568,4 +568,31 @@ private Mono<String> pushArtifactErrorRecovery(String pushResult, Artifact artif
         }
         return Mono.just(pushResult);
     }
+
+    /**
+     * File system implementation of fetching remote changes. equivalent to git fetch <ref-name>
+     * @param jsonTransformationDTO : DTO to create path and other ref related details
+     * @param gitAuth : authentication holder
+     * @return : returns string for remote fetch
+     */
+    @Override
+    public Mono<String> fetchRemoteChanges(ArtifactJsonTransformationDTO jsonTransformationDTO, GitAuth gitAuth) {
+
+        String workspaceId = jsonTransformationDTO.getWorkspaceId();
+        String baseArtifactId = jsonTransformationDTO.getBaseArtifactId();
+        String repoName = jsonTransformationDTO.getRepoName();
+        String refName = jsonTransformationDTO.getRefName();
+
+        ArtifactType artifactType = jsonTransformationDTO.getArtifactType();
+        GitArtifactHelper<?> gitArtifactHelper = gitArtifactHelperResolver.getArtifactHelper(artifactType);
+        Path repoSuffix = gitArtifactHelper.getRepoSuffixPath(workspaceId, baseArtifactId, repoName);
+
+        Path repoPath = fsGitHandler.createRepoPath(repoSuffix);
+        Mono<Boolean> checkoutBranchMono = fsGitHandler.checkoutToBranch(repoSuffix, refName);
+
+        Mono<String> fetchRemoteMono = fsGitHandler.fetchRemote(
+                repoPath, gitAuth.getPublicKey(), gitAuth.getPrivateKey(), true, refName, false);
+
+        return checkoutBranchMono.then(Mono.defer(() -> fetchRemoteMono));
+    }
 }

app/server/appsmith-server/src/main/java/com/appsmith/server/git/utils/GitAnalyticsUtils.java

@@ -5,6 +5,7 @@
 import com.appsmith.server.domains.ApplicationMode;
 import com.appsmith.server.domains.Artifact;
 import com.appsmith.server.domains.GitArtifactMetadata;
+import com.appsmith.server.domains.User;
 import com.appsmith.server.helpers.GitUtils;
 import com.appsmith.server.services.AnalyticsService;
 import com.appsmith.server.services.SessionUserService;
@@ -122,4 +123,27 @@ public Mono<? extends Artifact> addAnalyticsForGitOperation(
                 .sendEvent(event.getEventName(), user.getUsername(), analyticsProps)
                 .thenReturn(artifact));
     }
+
+    public Mono<Void> sendUnitExecutionTimeAnalyticsEvent(
+            String flowName, Long elapsedTime, User currentUser, Artifact artifact) {
+        GitArtifactMetadata gitArtifactMetadata = artifact.getGitArtifactMetadata();
+
+        final Map<String, Object> data = Map.of(
+                FieldName.FLOW_NAME,
+                flowName,
+                FieldName.APPLICATION_ID,
+                gitArtifactMetadata.getDefaultArtifactId(),
+                "appId",
+                gitArtifactMetadata.getDefaultArtifactId(),
+                FieldName.BRANCH_NAME,
+                gitArtifactMetadata.getBranchName(),
+                "organizationId",
+                artifact.getWorkspaceId(),
+                "repoUrl",
+                gitArtifactMetadata.getRemoteUrl(),
+                "executionTime",
+                elapsedTime);
+        return analyticsService.sendEvent(
+                AnalyticsEvents.UNIT_EXECUTION_TIME.getEventName(), currentUser.getUsername(), data);
+    }
 }