Documentation / glossary-content.txton commit Recommend git-filter-repo instead of git-filter-branch (9df53c5)
   1[[def_alternate_object_database]]alternate object database::
   2        Via the alternates mechanism, a <<def_repository,repository>>
   3        can inherit part of its <<def_object_database,object database>>
   4        from another object database, which is called an "alternate".
   5
   6[[def_bare_repository]]bare repository::
   7        A bare repository is normally an appropriately
   8        named <<def_directory,directory>> with a `.git` suffix that does not
   9        have a locally checked-out copy of any of the files under
  10        revision control. That is, all of the Git
  11        administrative and control files that would normally be present in the
  12        hidden `.git` sub-directory are directly present in the
  13        `repository.git` directory instead,
  14        and no other files are present and checked out. Usually publishers of
  15        public repositories make bare repositories available.
  16
  17[[def_blob_object]]blob object::
  18        Untyped <<def_object,object>>, e.g. the contents of a file.
  19
  20[[def_branch]]branch::
  21        A "branch" is an active line of development.  The most recent
  22        <<def_commit,commit>> on a branch is referred to as the tip of
  23        that branch.  The tip of the branch is referenced by a branch
  24        <<def_head,head>>, which moves forward as additional development
  25        is done on the branch.  A single Git
  26        <<def_repository,repository>> can track an arbitrary number of
  27        branches, but your <<def_working_tree,working tree>> is
  28        associated with just one of them (the "current" or "checked out"
  29        branch), and <<def_HEAD,HEAD>> points to that branch.
  30
  31[[def_cache]]cache::
  32        Obsolete for: <<def_index,index>>.
  33
  34[[def_chain]]chain::
  35        A list of objects, where each <<def_object,object>> in the list contains
  36        a reference to its successor (for example, the successor of a
  37        <<def_commit,commit>> could be one of its <<def_parent,parents>>).
  38
  39[[def_changeset]]changeset::
  40        BitKeeper/cvsps speak for "<<def_commit,commit>>". Since Git does not
  41        store changes, but states, it really does not make sense to use the term
  42        "changesets" with Git.
  43
  44[[def_checkout]]checkout::
  45        The action of updating all or part of the
  46        <<def_working_tree,working tree>> with a <<def_tree_object,tree object>>
  47        or <<def_blob_object,blob>> from the
  48        <<def_object_database,object database>>, and updating the
  49        <<def_index,index>> and <<def_HEAD,HEAD>> if the whole working tree has
  50        been pointed at a new <<def_branch,branch>>.
  51
  52[[def_cherry-picking]]cherry-picking::
  53        In <<def_SCM,SCM>> jargon, "cherry pick" means to choose a subset of
  54        changes out of a series of changes (typically commits) and record them
  55        as a new series of changes on top of a different codebase. In Git, this is
  56        performed by the "git cherry-pick" command to extract the change introduced
  57        by an existing <<def_commit,commit>> and to record it based on the tip
  58        of the current <<def_branch,branch>> as a new commit.
  59
  60[[def_clean]]clean::
  61        A <<def_working_tree,working tree>> is clean, if it
  62        corresponds to the <<def_revision,revision>> referenced by the current
  63        <<def_head,head>>. Also see "<<def_dirty,dirty>>".
  64
  65[[def_commit]]commit::
  66        As a noun: A single point in the
  67        Git history; the entire history of a project is represented as a
  68        set of interrelated commits.  The word "commit" is often
  69        used by Git in the same places other revision control systems
  70        use the words "revision" or "version".  Also used as a short
  71        hand for <<def_commit_object,commit object>>.
  72+
  73As a verb: The action of storing a new snapshot of the project's
  74state in the Git history, by creating a new commit representing the current
  75state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>>
  76to point at the new commit.
  77
  78[[def_commit_object]]commit object::
  79        An <<def_object,object>> which contains the information about a
  80        particular <<def_revision,revision>>, such as <<def_parent,parents>>, committer,
  81        author, date and the <<def_tree_object,tree object>> which corresponds
  82        to the top <<def_directory,directory>> of the stored
  83        revision.
  84
  85[[def_commit-ish]]commit-ish (also committish)::
  86        A <<def_commit_object,commit object>> or an
  87        <<def_object,object>> that can be recursively dereferenced to
  88        a commit object.
  89        The following are all commit-ishes:
  90        a commit object,
  91        a <<def_tag_object,tag object>> that points to a commit
  92        object,
  93        a tag object that points to a tag object that points to a
  94        commit object,
  95        etc.
  96
  97[[def_core_git]]core Git::
  98        Fundamental data structures and utilities of Git. Exposes only limited
  99        source code management tools.
 100
 101[[def_DAG]]DAG::
 102        Directed acyclic graph. The <<def_commit_object,commit objects>> form a
 103        directed acyclic graph, because they have parents (directed), and the
 104        graph of commit objects is acyclic (there is no <<def_chain,chain>>
 105        which begins and ends with the same <<def_object,object>>).
 106
 107[[def_dangling_object]]dangling object::
 108        An <<def_unreachable_object,unreachable object>> which is not
 109        <<def_reachable,reachable>> even from other unreachable objects; a
 110        dangling object has no references to it from any
 111        reference or <<def_object,object>> in the <<def_repository,repository>>.
 112
 113[[def_detached_HEAD]]detached HEAD::
 114        Normally the <<def_HEAD,HEAD>> stores the name of a
 115        <<def_branch,branch>>, and commands that operate on the
 116        history HEAD represents operate on the history leading to the
 117        tip of the branch the HEAD points at.  However, Git also
 118        allows you to <<def_checkout,check out>> an arbitrary
 119        <<def_commit,commit>> that isn't necessarily the tip of any
 120        particular branch.  The HEAD in such a state is called
 121        "detached".
 122+
 123Note that commands that operate on the history of the current branch
 124(e.g. `git commit` to build a new history on top of it) still work
 125while the HEAD is detached. They update the HEAD to point at the tip
 126of the updated history without affecting any branch.  Commands that
 127update or inquire information _about_ the current branch (e.g. `git
 128branch --set-upstream-to` that sets what remote-tracking branch the
 129current branch integrates with) obviously do not work, as there is no
 130(real) current branch to ask about in this state.
 131
 132[[def_directory]]directory::
 133        The list you get with "ls" :-)
 134
 135[[def_dirty]]dirty::
 136        A <<def_working_tree,working tree>> is said to be "dirty" if
 137        it contains modifications which have not been <<def_commit,committed>> to the current
 138        <<def_branch,branch>>.
 139
 140[[def_evil_merge]]evil merge::
 141        An evil merge is a <<def_merge,merge>> that introduces changes that
 142        do not appear in any <<def_parent,parent>>.
 143
 144[[def_fast_forward]]fast-forward::
 145        A fast-forward is a special type of <<def_merge,merge>> where you have a
 146        <<def_revision,revision>> and you are "merging" another
 147        <<def_branch,branch>>'s changes that happen to be a descendant of what
 148        you have. In such a case, you do not make a new <<def_merge,merge>>
 149        <<def_commit,commit>> but instead just update to his
 150        revision. This will happen frequently on a
 151        <<def_remote_tracking_branch,remote-tracking branch>> of a remote
 152        <<def_repository,repository>>.
 153
 154[[def_fetch]]fetch::
 155        Fetching a <<def_branch,branch>> means to get the
 156        branch's <<def_head_ref,head ref>> from a remote
 157        <<def_repository,repository>>, to find out which objects are
 158        missing from the local <<def_object_database,object database>>,
 159        and to get them, too.  See also linkgit:git-fetch[1].
 160
 161[[def_file_system]]file system::
 162        Linus Torvalds originally designed Git to be a user space file system,
 163        i.e. the infrastructure to hold files and directories. That ensured the
 164        efficiency and speed of Git.
 165
 166[[def_git_archive]]Git archive::
 167        Synonym for <<def_repository,repository>> (for arch people).
 168
 169[[def_gitfile]]gitfile::
 170        A plain file `.git` at the root of a working tree that
 171        points at the directory that is the real repository.
 172
 173[[def_grafts]]grafts::
 174        Grafts enables two otherwise different lines of development to be joined
 175        together by recording fake ancestry information for commits. This way
 176        you can make Git pretend the set of <<def_parent,parents>> a <<def_commit,commit>> has
 177        is different from what was recorded when the commit was
 178        created. Configured via the `.git/info/grafts` file.
 179+
 180Note that the grafts mechanism is outdated and can lead to problems
 181transferring objects between repositories; see linkgit:git-replace[1]
 182for a more flexible and robust system to do the same thing.
 183
 184[[def_hash]]hash::
 185        In Git's context, synonym for <<def_object_name,object name>>.
 186
 187[[def_head]]head::
 188        A <<def_ref,named reference>> to the <<def_commit,commit>> at the tip of a
 189        <<def_branch,branch>>.  Heads are stored in a file in
 190        `$GIT_DIR/refs/heads/` directory, except when using packed refs. (See
 191        linkgit:git-pack-refs[1].)
 192
 193[[def_HEAD]]HEAD::
 194        The current <<def_branch,branch>>.  In more detail: Your <<def_working_tree,
 195        working tree>> is normally derived from the state of the tree
 196        referred to by HEAD.  HEAD is a reference to one of the
 197        <<def_head,heads>> in your repository, except when using a
 198        <<def_detached_HEAD,detached HEAD>>, in which case it directly
 199        references an arbitrary commit.
 200
 201[[def_head_ref]]head ref::
 202        A synonym for <<def_head,head>>.
 203
 204[[def_hook]]hook::
 205        During the normal execution of several Git commands, call-outs are made
 206        to optional scripts that allow a developer to add functionality or
 207        checking. Typically, the hooks allow for a command to be pre-verified
 208        and potentially aborted, and allow for a post-notification after the
 209        operation is done. The hook scripts are found in the
 210        `$GIT_DIR/hooks/` directory, and are enabled by simply
 211        removing the `.sample` suffix from the filename. In earlier versions
 212        of Git you had to make them executable.
 213
 214[[def_index]]index::
 215        A collection of files with stat information, whose contents are stored
 216        as objects. The index is a stored version of your
 217        <<def_working_tree,working tree>>. Truth be told, it can also contain a second, and even
 218        a third version of a working tree, which are used
 219        when <<def_merge,merging>>.
 220
 221[[def_index_entry]]index entry::
 222        The information regarding a particular file, stored in the
 223        <<def_index,index>>. An index entry can be unmerged, if a
 224        <<def_merge,merge>> was started, but not yet finished (i.e. if
 225        the index contains multiple versions of that file).
 226
 227[[def_master]]master::
 228        The default development <<def_branch,branch>>. Whenever you
 229        create a Git <<def_repository,repository>>, a branch named
 230        "master" is created, and becomes the active branch. In most
 231        cases, this contains the local development, though that is
 232        purely by convention and is not required.
 233
 234[[def_merge]]merge::
 235        As a verb: To bring the contents of another
 236        <<def_branch,branch>> (possibly from an external
 237        <<def_repository,repository>>) into the current branch.  In the
 238        case where the merged-in branch is from a different repository,
 239        this is done by first <<def_fetch,fetching>> the remote branch
 240        and then merging the result into the current branch.  This
 241        combination of fetch and merge operations is called a
 242        <<def_pull,pull>>.  Merging is performed by an automatic process
 243        that identifies changes made since the branches diverged, and
 244        then applies all those changes together.  In cases where changes
 245        conflict, manual intervention may be required to complete the
 246        merge.
 247+
 248As a noun: unless it is a <<def_fast_forward,fast-forward>>, a
 249successful merge results in the creation of a new <<def_commit,commit>>
 250representing the result of the merge, and having as
 251<<def_parent,parents>> the tips of the merged <<def_branch,branches>>.
 252This commit is referred to as a "merge commit", or sometimes just a
 253"merge".
 254
 255[[def_object]]object::
 256        The unit of storage in Git. It is uniquely identified by the
 257        <<def_SHA1,SHA-1>> of its contents. Consequently, an
 258        object cannot be changed.
 259
 260[[def_object_database]]object database::
 261        Stores a set of "objects", and an individual <<def_object,object>> is
 262        identified by its <<def_object_name,object name>>. The objects usually
 263        live in `$GIT_DIR/objects/`.
 264
 265[[def_object_identifier]]object identifier::
 266        Synonym for <<def_object_name,object name>>.
 267
 268[[def_object_name]]object name::
 269        The unique identifier of an <<def_object,object>>.  The
 270        object name is usually represented by a 40 character
 271        hexadecimal string.  Also colloquially called <<def_SHA1,SHA-1>>.
 272
 273[[def_object_type]]object type::
 274        One of the identifiers "<<def_commit_object,commit>>",
 275        "<<def_tree_object,tree>>", "<<def_tag_object,tag>>" or
 276        "<<def_blob_object,blob>>" describing the type of an
 277        <<def_object,object>>.
 278
 279[[def_octopus]]octopus::
 280        To <<def_merge,merge>> more than two <<def_branch,branches>>.
 281
 282[[def_origin]]origin::
 283        The default upstream <<def_repository,repository>>. Most projects have
 284        at least one upstream project which they track. By default
 285        'origin' is used for that purpose. New upstream updates
 286        will be fetched into <<def_remote_tracking_branch,remote-tracking branches>> named
 287        origin/name-of-upstream-branch, which you can see using
 288        `git branch -r`.
 289
 290[[def_overlay]]overlay::
 291        Only update and add files to the working directory, but don't
 292        delete them, similar to how 'cp -R' would update the contents
 293        in the destination directory.  This is the default mode in a
 294        <<def_checkout,checkout>> when checking out files from the
 295        <<def_index,index>> or a <<def_tree-ish,tree-ish>>.  In
 296        contrast, no-overlay mode also deletes tracked files not
 297        present in the source, similar to 'rsync --delete'.
 298
 299[[def_pack]]pack::
 300        A set of objects which have been compressed into one file (to save space
 301        or to transmit them efficiently).
 302
 303[[def_pack_index]]pack index::
 304        The list of identifiers, and other information, of the objects in a
 305        <<def_pack,pack>>, to assist in efficiently accessing the contents of a
 306        pack.
 307
 308[[def_pathspec]]pathspec::
 309        Pattern used to limit paths in Git commands.
 310+
 311Pathspecs are used on the command line of "git ls-files", "git
 312ls-tree", "git add", "git grep", "git diff", "git checkout",
 313and many other commands to
 314limit the scope of operations to some subset of the tree or
 315worktree.  See the documentation of each command for whether
 316paths are relative to the current directory or toplevel.  The
 317pathspec syntax is as follows:
 318+
 319--
 320
 321* any path matches itself
 322* the pathspec up to the last slash represents a
 323  directory prefix.  The scope of that pathspec is
 324  limited to that subtree.
 325* the rest of the pathspec is a pattern for the remainder
 326  of the pathname.  Paths relative to the directory
 327  prefix will be matched against that pattern using fnmatch(3);
 328  in particular, '*' and '?' _can_ match directory separators.
 329
 330--
 331+
 332For example, Documentation/*.jpg will match all .jpg files
 333in the Documentation subtree,
 334including Documentation/chapter_1/figure_1.jpg.
 335+
 336A pathspec that begins with a colon `:` has special meaning.  In the
 337short form, the leading colon `:` is followed by zero or more "magic
 338signature" letters (which optionally is terminated by another colon `:`),
 339and the remainder is the pattern to match against the path.
 340The "magic signature" consists of ASCII symbols that are neither
 341alphanumeric, glob, regex special characters nor colon.
 342The optional colon that terminates the "magic signature" can be
 343omitted if the pattern begins with a character that does not belong to
 344"magic signature" symbol set and is not a colon.
 345+
 346In the long form, the leading colon `:` is followed by an open
 347parenthesis `(`, a comma-separated list of zero or more "magic words",
 348and a close parentheses `)`, and the remainder is the pattern to match
 349against the path.
 350+
 351A pathspec with only a colon means "there is no pathspec". This form
 352should not be combined with other pathspec.
 353+
 354--
 355top;;
 356        The magic word `top` (magic signature: `/`) makes the pattern
 357        match from the root of the working tree, even when you are
 358        running the command from inside a subdirectory.
 359
 360literal;;
 361        Wildcards in the pattern such as `*` or `?` are treated
 362        as literal characters.
 363
 364icase;;
 365        Case insensitive match.
 366
 367glob;;
 368        Git treats the pattern as a shell glob suitable for
 369        consumption by fnmatch(3) with the FNM_PATHNAME flag:
 370        wildcards in the pattern will not match a / in the pathname.
 371        For example, "Documentation/{asterisk}.html" matches
 372        "Documentation/git.html" but not "Documentation/ppc/ppc.html"
 373        or "tools/perf/Documentation/perf.html".
 374+
 375Two consecutive asterisks ("`**`") in patterns matched against
 376full pathname may have special meaning:
 377
 378 - A leading "`**`" followed by a slash means match in all
 379   directories. For example, "`**/foo`" matches file or directory
 380   "`foo`" anywhere, the same as pattern "`foo`". "`**/foo/bar`"
 381   matches file or directory "`bar`" anywhere that is directly
 382   under directory "`foo`".
 383
 384 - A trailing "`/**`" matches everything inside. For example,
 385   "`abc/**`" matches all files inside directory "abc", relative
 386   to the location of the `.gitignore` file, with infinite depth.
 387
 388 - A slash followed by two consecutive asterisks then a slash
 389   matches zero or more directories. For example, "`a/**/b`"
 390   matches "`a/b`", "`a/x/b`", "`a/x/y/b`" and so on.
 391
 392 - Other consecutive asterisks are considered invalid.
 393+
 394Glob magic is incompatible with literal magic.
 395
 396attr;;
 397After `attr:` comes a space separated list of "attribute
 398requirements", all of which must be met in order for the
 399path to be considered a match; this is in addition to the
 400usual non-magic pathspec pattern matching.
 401See linkgit:gitattributes[5].
 402+
 403Each of the attribute requirements for the path takes one of
 404these forms:
 405
 406- "`ATTR`" requires that the attribute `ATTR` be set.
 407
 408- "`-ATTR`" requires that the attribute `ATTR` be unset.
 409
 410- "`ATTR=VALUE`" requires that the attribute `ATTR` be
 411  set to the string `VALUE`.
 412
 413- "`!ATTR`" requires that the attribute `ATTR` be
 414  unspecified.
 415+
 416Note that when matching against a tree object, attributes are still
 417obtained from working tree, not from the given tree object.
 418
 419exclude;;
 420        After a path matches any non-exclude pathspec, it will be run
 421        through all exclude pathspecs (magic signature: `!` or its
 422        synonym `^`). If it matches, the path is ignored.  When there
 423        is no non-exclude pathspec, the exclusion is applied to the
 424        result set as if invoked without any pathspec.
 425--
 426
 427[[def_parent]]parent::
 428        A <<def_commit_object,commit object>> contains a (possibly empty) list
 429        of the logical predecessor(s) in the line of development, i.e. its
 430        parents.
 431
 432[[def_pickaxe]]pickaxe::
 433        The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore
 434        routines that help select changes that add or delete a given text
 435        string. With the `--pickaxe-all` option, it can be used to view the full
 436        <<def_changeset,changeset>> that introduced or removed, say, a
 437        particular line of text. See linkgit:git-diff[1].
 438
 439[[def_plumbing]]plumbing::
 440        Cute name for <<def_core_git,core Git>>.
 441
 442[[def_porcelain]]porcelain::
 443        Cute name for programs and program suites depending on
 444        <<def_core_git,core Git>>, presenting a high level access to
 445        core Git. Porcelains expose more of a <<def_SCM,SCM>>
 446        interface than the <<def_plumbing,plumbing>>.
 447
 448[[def_per_worktree_ref]]per-worktree ref::
 449        Refs that are per-<<def_working_tree,worktree>>, rather than
 450        global.  This is presently only <<def_HEAD,HEAD>> and any refs
 451        that start with `refs/bisect/`, but might later include other
 452        unusual refs.
 453
 454[[def_pseudoref]]pseudoref::
 455        Pseudorefs are a class of files under `$GIT_DIR` which behave
 456        like refs for the purposes of rev-parse, but which are treated
 457        specially by git.  Pseudorefs both have names that are all-caps,
 458        and always start with a line consisting of a
 459        <<def_SHA1,SHA-1>> followed by whitespace.  So, HEAD is not a
 460        pseudoref, because it is sometimes a symbolic ref.  They might
 461        optionally contain some additional data.  `MERGE_HEAD` and
 462        `CHERRY_PICK_HEAD` are examples.  Unlike
 463        <<def_per_worktree_ref,per-worktree refs>>, these files cannot
 464        be symbolic refs, and never have reflogs.  They also cannot be
 465        updated through the normal ref update machinery.  Instead,
 466        they are updated by directly writing to the files.  However,
 467        they can be read as if they were refs, so `git rev-parse
 468        MERGE_HEAD` will work.
 469
 470[[def_pull]]pull::
 471        Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and
 472        <<def_merge,merge>> it.  See also linkgit:git-pull[1].
 473
 474[[def_push]]push::
 475        Pushing a <<def_branch,branch>> means to get the branch's
 476        <<def_head_ref,head ref>> from a remote <<def_repository,repository>>,
 477        find out if it is an ancestor to the branch's local
 478        head ref, and in that case, putting all
 479        objects, which are <<def_reachable,reachable>> from the local
 480        head ref, and which are missing from the remote
 481        repository, into the remote
 482        <<def_object_database,object database>>, and updating the remote
 483        head ref. If the remote <<def_head,head>> is not an
 484        ancestor to the local head, the push fails.
 485
 486[[def_reachable]]reachable::
 487        All of the ancestors of a given <<def_commit,commit>> are said to be
 488        "reachable" from that commit. More
 489        generally, one <<def_object,object>> is reachable from
 490        another if we can reach the one from the other by a <<def_chain,chain>>
 491        that follows <<def_tag,tags>> to whatever they tag,
 492        <<def_commit_object,commits>> to their parents or trees, and
 493        <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>>
 494        that they contain.
 495
 496[[def_rebase]]rebase::
 497        To reapply a series of changes from a <<def_branch,branch>> to a
 498        different base, and reset the <<def_head,head>> of that branch
 499        to the result.
 500
 501[[def_ref]]ref::
 502        A name that begins with `refs/` (e.g. `refs/heads/master`)
 503        that points to an <<def_object_name,object name>> or another
 504        ref (the latter is called a <<def_symref,symbolic ref>>).
 505        For convenience, a ref can sometimes be abbreviated when used
 506        as an argument to a Git command; see linkgit:gitrevisions[7]
 507        for details.
 508        Refs are stored in the <<def_repository,repository>>.
 509+
 510The ref namespace is hierarchical.
 511Different subhierarchies are used for different purposes (e.g. the
 512`refs/heads/` hierarchy is used to represent local branches).
 513+
 514There are a few special-purpose refs that do not begin with `refs/`.
 515The most notable example is `HEAD`.
 516
 517[[def_reflog]]reflog::
 518        A reflog shows the local "history" of a ref.  In other words,
 519        it can tell you what the 3rd last revision in _this_ repository
 520        was, and what was the current state in _this_ repository,
 521        yesterday 9:14pm.  See linkgit:git-reflog[1] for details.
 522
 523[[def_refspec]]refspec::
 524        A "refspec" is used by <<def_fetch,fetch>> and
 525        <<def_push,push>> to describe the mapping between remote
 526        <<def_ref,ref>> and local ref.
 527
 528[[def_remote]]remote repository::
 529        A <<def_repository,repository>> which is used to track the same
 530        project but resides somewhere else. To communicate with remotes,
 531        see <<def_fetch,fetch>> or <<def_push,push>>.
 532
 533[[def_remote_tracking_branch]]remote-tracking branch::
 534        A <<def_ref,ref>> that is used to follow changes from another
 535        <<def_repository,repository>>. It typically looks like
 536        'refs/remotes/foo/bar' (indicating that it tracks a branch named
 537        'bar' in a remote named 'foo'), and matches the right-hand-side of
 538        a configured fetch <<def_refspec,refspec>>. A remote-tracking
 539        branch should not contain direct modifications or have local
 540        commits made to it.
 541
 542[[def_repository]]repository::
 543        A collection of <<def_ref,refs>> together with an
 544        <<def_object_database,object database>> containing all objects
 545        which are <<def_reachable,reachable>> from the refs, possibly
 546        accompanied by meta data from one or more <<def_porcelain,porcelains>>. A
 547        repository can share an object database with other repositories
 548        via <<def_alternate_object_database,alternates mechanism>>.
 549
 550[[def_resolve]]resolve::
 551        The action of fixing up manually what a failed automatic
 552        <<def_merge,merge>> left behind.
 553
 554[[def_revision]]revision::
 555        Synonym for <<def_commit,commit>> (the noun).
 556
 557[[def_rewind]]rewind::
 558        To throw away part of the development, i.e. to assign the
 559        <<def_head,head>> to an earlier <<def_revision,revision>>.
 560
 561[[def_SCM]]SCM::
 562        Source code management (tool).
 563
 564[[def_SHA1]]SHA-1::
 565        "Secure Hash Algorithm 1"; a cryptographic hash function.
 566        In the context of Git used as a synonym for <<def_object_name,object name>>.
 567
 568[[def_shallow_clone]]shallow clone::
 569        Mostly a synonym to <<def_shallow_repository,shallow repository>>
 570        but the phrase makes it more explicit that it was created by
 571        running `git clone --depth=...` command.
 572
 573[[def_shallow_repository]]shallow repository::
 574        A shallow <<def_repository,repository>> has an incomplete
 575        history some of whose <<def_commit,commits>> have <<def_parent,parents>> cauterized away (in other
 576        words, Git is told to pretend that these commits do not have the
 577        parents, even though they are recorded in the <<def_commit_object,commit
 578        object>>). This is sometimes useful when you are interested only in the
 579        recent history of a project even though the real history recorded in the
 580        upstream is much larger. A shallow repository
 581        is created by giving the `--depth` option to linkgit:git-clone[1], and
 582        its history can be later deepened with linkgit:git-fetch[1].
 583
 584[[def_stash]]stash entry::
 585        An <<def_object,object>> used to temporarily store the contents of a
 586        <<def_dirty,dirty>> working directory and the index for future reuse.
 587
 588[[def_submodule]]submodule::
 589        A <<def_repository,repository>> that holds the history of a
 590        separate project inside another repository (the latter of
 591        which is called <<def_superproject, superproject>>).
 592
 593[[def_superproject]]superproject::
 594        A <<def_repository,repository>> that references repositories
 595        of other projects in its working tree as <<def_submodule,submodules>>.
 596        The superproject knows about the names of (but does not hold
 597        copies of) commit objects of the contained submodules.
 598
 599[[def_symref]]symref::
 600        Symbolic reference: instead of containing the <<def_SHA1,SHA-1>>
 601        id itself, it is of the format 'ref: refs/some/thing' and when
 602        referenced, it recursively dereferences to this reference.
 603        '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic
 604        references are manipulated with the linkgit:git-symbolic-ref[1]
 605        command.
 606
 607[[def_tag]]tag::
 608        A <<def_ref,ref>> under `refs/tags/` namespace that points to an
 609        object of an arbitrary type (typically a tag points to either a
 610        <<def_tag_object,tag>> or a <<def_commit_object,commit object>>).
 611        In contrast to a <<def_head,head>>, a tag is not updated by
 612        the `commit` command. A Git tag has nothing to do with a Lisp
 613        tag (which would be called an <<def_object_type,object type>>
 614        in Git's context). A tag is most typically used to mark a particular
 615        point in the commit ancestry <<def_chain,chain>>.
 616
 617[[def_tag_object]]tag object::
 618        An <<def_object,object>> containing a <<def_ref,ref>> pointing to
 619        another object, which can contain a message just like a
 620        <<def_commit_object,commit object>>. It can also contain a (PGP)
 621        signature, in which case it is called a "signed tag object".
 622
 623[[def_topic_branch]]topic branch::
 624        A regular Git <<def_branch,branch>> that is used by a developer to
 625        identify a conceptual line of development. Since branches are very easy
 626        and inexpensive, it is often desirable to have several small branches
 627        that each contain very well defined concepts or small incremental yet
 628        related changes.
 629
 630[[def_tree]]tree::
 631        Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree
 632        object>> together with the dependent <<def_blob_object,blob>> and tree objects
 633        (i.e. a stored representation of a working tree).
 634
 635[[def_tree_object]]tree object::
 636        An <<def_object,object>> containing a list of file names and modes along
 637        with refs to the associated blob and/or tree objects. A
 638        <<def_tree,tree>> is equivalent to a <<def_directory,directory>>.
 639
 640[[def_tree-ish]]tree-ish (also treeish)::
 641        A <<def_tree_object,tree object>> or an <<def_object,object>>
 642        that can be recursively dereferenced to a tree object.
 643        Dereferencing a <<def_commit_object,commit object>> yields the
 644        tree object corresponding to the <<def_revision,revision>>'s
 645        top <<def_directory,directory>>.
 646        The following are all tree-ishes:
 647        a <<def_commit-ish,commit-ish>>,
 648        a tree object,
 649        a <<def_tag_object,tag object>> that points to a tree object,
 650        a tag object that points to a tag object that points to a tree
 651        object,
 652        etc.
 653
 654[[def_unmerged_index]]unmerged index::
 655        An <<def_index,index>> which contains unmerged
 656        <<def_index_entry,index entries>>.
 657
 658[[def_unreachable_object]]unreachable object::
 659        An <<def_object,object>> which is not <<def_reachable,reachable>> from a
 660        <<def_branch,branch>>, <<def_tag,tag>>, or any other reference.
 661
 662[[def_upstream_branch]]upstream branch::
 663        The default <<def_branch,branch>> that is merged into the branch in
 664        question (or the branch in question is rebased onto). It is configured
 665        via branch.<name>.remote and branch.<name>.merge. If the upstream branch
 666        of 'A' is 'origin/B' sometimes we say "'A' is tracking 'origin/B'".
 667
 668[[def_working_tree]]working tree::
 669        The tree of actual checked out files.  The working tree normally
 670        contains the contents of the <<def_HEAD,HEAD>> commit's tree,
 671        plus any local changes that you have made but not yet committed.