book

Git: Mastering Version Control

by Ferdinando Santacroce, Aske Olsson, Rasmus Voss, Jakub Narębski

October 2016

Beginner

861 pages

20h 37m

English

Packt Publishing

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What this learning path covers
Downloading the example codeErrataPiracyQuestions

Installing Git
Setting up a new repositoryAdding a fileCommit the added fileModify a committed file
Repository structure and file status life cycleThe working directoryFile statusesThe staging areaUnstaging a fileThe time metaphorThe pastThe presentThe future
Unstaging a file
Anatomy of a commitThe commit snapshotThe commit hashAuthor, e-mail, and dateCommit messagesCommitting a bunch of filesIgnoring some files and folders by defaultHighlighting an important commit – Git tags
Anatomy of branchesLooking at the current branchesCreating a new branchSwitching from branch to branchUnderstanding what happens under the hoodA bird's eye view to branchesTyping is boring – Git aliasesMerging branchesMerge is not the end of the branchExercisesExercise 2.1What you will learnScenarioResultsExercise 2.2What you will learnScenarioResultsDeal with branches' modificationsDiffing branchesUsing a visual diff toolResolving merge conflictsEdit collisionsResolving a removed file conflictKeeping the edited fileResolving conflicts by removing the file
Working with remotesSetting up a new GitHub accountCloning a repositoryUploading modifications to remotesWhat do I send to the remote when I push?Pushing a new branch to the remoteThe originTracking branchesDownloading remote changesChecking for modifications and downloading themApplying downloaded changesGoing backward: publish a local repository to GitHubAdding a remote to a local repositoryPushing a local branch to a remote repositorySocial coding – collaborate using GitHubForking a repositorySubmitting pull requestsCreating a pull request
Dissecting the Git configurationConfiguration architectureConfiguration levelsSystem levelGlobal levelRepository levelListing configurationsEditing configuration files manuallySetting up other environment configurationsBasic configurationsTypos autocorrectionPush defaultDefining the default editorOther configurations
Shortcuts to common commandsCreating commandsgit unstagegit undogit lastgit difflastAdvanced aliases with external commandsRemoving an aliasAliasing the git command itself
Symbolic referencesAncestry referencesThe first parentThe second parent
Changing the last commit messageTracing changes in a fileCherry picking
Bare repositoriesConverting a regular repository to a bare oneBackup repositoriesArchiving the repositoryBundling the repository
The art of committingBuilding the right commitMake only one change per commitSplit up features and tasksWrite commit messages before starting to codeInclude the whole change in one commitDescribe the change, not what you have doneDon't be afraid to commitIsolate meaningless commitsThe perfect commit messageWriting a meaningful subjectAdding bulleted details lines, when neededTie other useful informationSpecial messages for releasesConclusions
Centralized workflowsHow they workFeature branch workflowGitFlowThe master branchHotfixes branchesThe develop branchThe release branchThe feature branchesConclusionThe GitHub flowAnything in the master branch is deployableCreating descriptive branches off of the masterPushing to named branches constantlyOpening a pull request at any timeMerging only after a pull request reviewDeploying immediately after reviewConclusionsOther workflowsThe Linux kernel workflow
Before startingPrerequisites
Creating a local Subversion repositoryChecking out the Subversion repository with svn clientCloning a Subversion repository from GitSetting up a local Subversion serverAdding a tag and a branchCommitting a file to Subversion using Git as a client
Retrieving the list of Subversion usersCloning the Subversion repositoryPreserving the ignored file listPushing to a local bare Git repositoryArranging branches and tagsRenaming the trunk branch to masterConverting Subversion tags to Git tagsPushing the local repository to a remote
Git GUI clientsWindowsGit GUITortoiseGitGitHub for WindowsAtlassian SourceTreeCmderMac OS XLinux
The SCM Manager
Git community on Google+GitMinutes and Thomas Ferris Nicolaisen's blogFerdinando Santacroce's blog
Introduction
Getting readyHow to do it...The commit objectThe tree objectThe blob objectThe branchThe tag objectHow it works...There's more...See also
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An introduction to version control and Git
Repository setupCreating a Git repositoryCloning the repository and creating the first commitPublishing changesExamining history and viewing changesRenaming and moving filesUpdating your repository (with merge)Creating a tagResolving a merge conflictAdding files in bulk and removing filesUndoing changes to a fileCreating a new branchMerging a branch (no conflicts)Undoing an unpublished merge
Directed Acyclic GraphsWhole-tree commitsBranches and tagsBranch pointsMerge commits
HEAD – the implicit revisionBranch and tag referencesSHA-1 and the shortened SHA-1 identifierAncestry referencesReverse ancestry references: the git describe outputReflog shortnamesUpstream of remote-tracking branchesSelecting revision by the commit message
Single revision as a revision rangeDouble dot notationMultiple points – including and excluding revisionsThe revision range for a single revisionTriple-dot notation
Limiting the number of revisionsMatching revision metadataTime-limiting optionsMatching commit contentsCommit parentsSearching changes in revisionsSelecting types of change
Path limitingHistory simplificationBlame – the line-wise history of a file
Predefined and user defined output formatsIncluding, formatting, and summing up changesSummarizing contributionsViewing a revision and a file at revision
Creating a new commitThe DAG view of creating a new commitThe index – a staging area for commitsExamining the changes to be committedThe status of the working directoryExamining differences from the last revisionUnified Git diff formatSelective commitSelecting files to commitInteractively selecting changesCreating a commit step by stepAmending a commit
Creating a new branchCreating orphan branchesSelecting and switching to a branchObstacles to switching to a branchAnonymous branchesGit checkout DWIM-meryListing branchesRewinding or resetting a branchDeleting a branchChanging the branch name
Ignoring filesMarking files as intentionally untrackedWhich types of file should be ignored?Listing ignored filesIgnoring changes in tracked files
Identifying binary files and end-of-line conversionsDiff and merge configurationGenerating diffs and binary filesConfiguring diff outputPerforming a 3-way mergeTransforming files (content filtering)Obligatory file transformationsKeyword expansion and substitutionOther built-in attributesDefining attribute macros
Rewinding the branch head, softlyRemoving or amending a commitSquashing commits with resetResetting the branch head and the indexSplitting a commit with resetSaving and restoring state with the WIP commitDiscarding changes and rewinding branchMoving commits to a feature branchUndoing a merge or a pullSafer reset – keeping your changesRebase changes to an earlier revision
Using git stashStash and the staging areaStash internalsUn-applying a stashRecovering stashes that were dropped erroneously
Examining files and directoriesSearching file contentsUn-tracking, un-staging, and un-modifying filesResetting a file to the old versionCleaning the working area
Collaborative workflowsBare repositoriesInteracting with other repositoriesThe centralized workflowThe peer-to-peer or forking workflowThe maintainer or integration manager workflowThe hierarchical or dictator and lieutenants workflows
The origin remoteListing and examining remotesAdding a new remoteUpdating information about remotesRenaming remotesChanging the remote URLsChanging the list of branches tracked by remoteSetting the default branch of remoteDeleting remote-tracking branchesSupport for triangular workflows
Local transportSmart transportsNative Git protocolSSH protocolSmart HTTP(S) protocolOffline transport with bundlesCloning and updating with bundleUsing bundle to update an existing repositoryUtilizing bundle to help with the initial cloneRemote transport helpersTransport relay with remote helpersUsing foreign SCM repositories as remotesCredentials/password managementAsking for passwordsPublic key authentication for SSHCredential helpers
Pushing to a public repositoryGenerating a pull requestExchanging patches
Content-addressed storageLightweight, annotated, and signed tagsLightweight tagsAnnotated tagsSigned tagsPublishing tagsTag verificationSigned commitsMerging signed tags (merge tags)
Types and purposes of branchesLong-running, perpetual branchesIntegration, graduation, or progressive-stability branchesPer-release branches and per-release maintenanceHotfix branches for security fixesPer-customer or per-deployment branchesAutomation branchesMob branches for anonymous push accessThe orphan branch trickShort-lived branchesTopic or feature branchesBugfix branchesDetached HEAD – the anonymous branch
The release and trunk branches workflowThe graduation, or progressive-stability branches workflowThe topic branches workflowGraduation branches in a topic branch workflowBranch management for a release in a topic branch workflowGit-flow – a successful Git branching modelFixing a security issue
Upstream and downstreamRemote-tracking branches and refspecRemote-tracking branchesRefspec – remote to local branch mapping specificationFetching and pulling versus pushingPull – fetch and update current branchPushing to the current branch in a nonbare remote repositoryThe default fetch refspec and push modesFetching and pushing branches and tagsFetching branchesFetching tags and automatic tag followingPushing branches and tagsPush modes and their useThe simple push mode – the defaultThe matching push mode for maintainersThe upstream push mode for the centralized workflowThe current push mode for the blessed repository workflow
Methods of combining changesMerging branchesNo divergence – fast-forward and up-to-date casesCreating a merge commitMerge strategies and their optionsReminder – merge driversReminder – signing merges and merging tagsCopying and applying a changesetCherry-pick – creating a copy of a changesetRevert – undoing an effect of a commitApplying a series of commits from patchesCherry-picking and reverting a mergeRebasing a branchMerge versus rebaseTypes of rebaseAdvanced rebasing techniques
The three-way mergeExamining failed mergesConflict markers in the worktreeThree stages in the indexExamining differences – the combined diff formatHow do we get there: git log --mergeAvoiding merge conflictsUseful merge optionsRerere – reuse recorded resolutionsDealing with merge conflictsAborting a mergeSelecting ours or theirs versionScriptable fixes – manual file remergingUsing graphical merge toolsMarking files as resolved and finalizing mergesResolving rebase conflictsgit-imerge – incremental merge and rebase for git
An introduction to Git internalsGit objectsThe plumbing and porcelain Git commandsEnvironment variables used by GitEnvironment variables affecting global behaviorEnvironment variables affecting repository locationsEnvironment variables affecting committing
Amending the last commitAn interactive rebaseReordering, removing, and fixing commitsSquashing commitsSplitting commitsTesting each rebased commitExternal tools – patch management interfacesScripted rewrite with the git filter-branchRunning the filter-branch without filtersAvailable filter types for filter-branch and their useExamples of using the git filter-branchExternal tools for large-scale history rewritingRemoving files from the history with BFG Repo CleanerEditing the repository history with reposurgeonThe perils of rewriting published historyThe consequences of upstream rewriteRecovering from an upstream history rewrite
Reverting a commitReverting a faulty mergeRecovering from reverted mergesStoring additional information with notesAdding notes to a commitHow notes are storedOther categories and uses of notesRewriting history and notesPublishing and retrieving notesUsing the replacements mechanismThe replacements mechanismExample – joining histories with git replaceHistorical note – graftsPublishing and retrieving replacements
Managing library and framework dependenciesManaging dependencies outside GitManually importing the code into your projectA Git subtree for embedding the subproject codeCreating a remote for a subprojectAdding a subproject as a subtreeCloning and updating superprojects with subtreesGetting updates from subprojects with a subtree mergeShowing changes between a subtree and its upstreamSending changes to the upstream of a subtreeThe Git submodules solution: repository inside repositoryGitlinks, .git files, and the git submodule commandAdding a subproject as a submoduleCloning superprojects with submodulesUpdating submodules after superproject changesExamining changes in a submoduleGetting updates from the upstream of the submoduleSending submodule changes upstreamTransforming a subfolder into a subtree or submoduleSubtrees versus submodulesUse cases for subtreesUse cases for submodulesThird-party subproject management solutions
Handling repositories with a very long historyUsing shallow clones to get truncated historyCloning only a single branchHandling repositories with large binary filesSplitting the binary asset folder into a separate submoduleStoring large binary files outside the repository
Git on the command lineGit-aware command promptCommand-line completion for GitAutocorrection for Git commandsMaking the command line prettierAlternative command line
Types of graphical toolsGraphical diff and merge toolsGraphical interface examples
Command-line options and environment variablesGit configuration filesThe syntax of Git configuration filesAccessing the Git configurationBasic client-side configurationThe rebase and merge setup, configuring pullPreserving undo information – the expiry of objectsFormatting and whitespaceServer-side configurationPer-file configuration with gitattributes
Installing a Git hookA template for repositoriesClient-side hooksCommit process hooksHooks for applying patches from e-mailsOther client-side hooksServer-side hooks
Command aliases for GitAdding new Git commandsCredential helpers and remote helpers
Repository maintenance
Recovering a lost commitTroubleshooting Git
Server-side hooksThe pre-receive hookPush-to-update hook for pushing to nonbare repositoriesThe update hookThe post-receive hookThe post-update hook (legacy mechanism)Using hooks to implement the Git-enforced policyEnforcing the policy with server-side hooksEarly notices about policy violations with client-side hooksSigned pushesServing Git repositoriesLocal protocolSSH protocolAnonymous Git protocolSmart HTTP(S) protocolDumb protocolsRemote helpersTools to manage Git repositoriesTips and tricks for hosting repositoriesReducing the size taken by repositoriesSpeeding up smart protocols with pack bitmapsSolving the large nonresumable initial clone problem
Starting a projectDividing work into repositoriesSelecting the collaboration workflowChoosing which files to keep under version control
Working on a topic branchDeciding what to base your work onSplitting changes into logically separate stepsWriting a good commit messagePreparing changes for submission
Submitting and describing changesThe art of the change reviewResponding to reviews and comments
Don't panic, recovery is almost always possibleDon't change the published historyNumbering and tagging releasesAutomate what is possible

Content preview from Git: Mastering Version Control

Rebasing commits to another branch

To start with, we are going to perform a very simple rebase where we will introduce a new file, commit this file, make a change to it, and then commit it again so that we end up with 2 new commits.

Getting ready

Before we start, we need a repository to work in. You can use a previous clone of jgit, but to get a close to identical output from the example, you can clone the jgit repository.

The jgit repository can be cloned as follows:

$ git clone https://git.eclipse.org/r/jgit/jgit chapter4
$ cd chapter4

How to do it…

We start by creating a local branch and then make two commits by performing the following steps; these are the commits that we want to rebase onto another branch: