1GIT Glossary 2============ 3 4[[def_alternate_object_database]]alternate object database:: 5 Via the alternates mechanism, a <<def_repository,repository>> 6 can inherit part of its <<def_object_database,object database>> 7 from another object database, which is called "alternate". 8 9[[def_bare_repository]]bare repository:: 10 A bare repository is normally an appropriately 11 named <<def_directory,directory>> with a `.git` suffix that does not 12 have a locally checked-out copy of any of the files under 13 revision control. That is, all of the `git` 14 administrative and control files that would normally be present in the 15 hidden `.git` sub-directory are directly present in the 16 `repository.git` directory instead, 17 and no other files are present and checked out. Usually publishers of 18 public repositories make bare repositories available. 19 20[[def_blob_object]]blob object:: 21 Untyped <<def_object,object>>, e.g. the contents of a file. 22 23[[def_branch]]branch:: 24 A "branch" is an active line of development. The most recent 25 <<def_commit,commit>> on a branch is referred to as the tip of 26 that branch. The tip of the branch is referenced by a branch 27 <<def_head,head>>, which moves forward as additional development 28 is done on the branch. A single git 29 <<def_repository,repository>> can track an arbitrary number of 30 branches, but your <<def_working_tree,working tree>> is 31 associated with just one of them (the "current" or "checked out" 32 branch), and <<def_HEAD,HEAD>> points to that branch. 33 34[[def_cache]]cache:: 35 Obsolete for: <<def_index,index>>. 36 37[[def_chain]]chain:: 38 A list of objects, where each <<def_object,object>> in the list contains 39 a reference to its successor (for example, the successor of a 40 <<def_commit,commit>> could be one of its <<def_parent,parents>>). 41 42[[def_changeset]]changeset:: 43 BitKeeper/cvsps speak for "<<def_commit,commit>>". Since git does not 44 store changes, but states, it really does not make sense to use the term 45 "changesets" with git. 46 47[[def_checkout]]checkout:: 48 The action of updating all or part of the 49 <<def_working_tree,working tree>> with a <<def_tree_object,tree object>> 50 or <<def_blob_object,blob>> from the 51 <<def_object_database,object database>>, and updating the 52 <<def_index,index>> and <<def_HEAD,HEAD>> if the whole working tree has 53 been pointed at a new <<def_branch,branch>>. 54 55[[def_cherry-picking]]cherry-picking:: 56 In <<def_SCM,SCM>> jargon, "cherry pick" means to choose a subset of 57 changes out of a series of changes (typically commits) and record them 58 as a new series of changes on top of a different codebase. In GIT, this is 59 performed by the "git cherry-pick" command to extract the change introduced 60 by an existing <<def_commit,commit>> and to record it based on the tip 61 of the current <<def_branch,branch>> as a new commit. 62 63[[def_clean]]clean:: 64 A <<def_working_tree,working tree>> is clean, if it 65 corresponds to the <<def_revision,revision>> referenced by the current 66 <<def_head,head>>. Also see "<<def_dirty,dirty>>". 67 68[[def_commit]]commit:: 69 As a noun: A single point in the 70 git history; the entire history of a project is represented as a 71 set of interrelated commits. The word "commit" is often 72 used by git in the same places other revision control systems 73 use the words "revision" or "version". Also used as a short 74 hand for <<def_commit_object,commit object>>. 75+ 76As a verb: The action of storing a new snapshot of the project's 77state in the git history, by creating a new commit representing the current 78state of the <<def_index,index>> and advancing <<def_HEAD,HEAD>> 79to point at the new commit. 80 81[[def_commit_object]]commit object:: 82 An <<def_object,object>> which contains the information about a 83 particular <<def_revision,revision>>, such as <<def_parent,parents>>, committer, 84 author, date and the <<def_tree_object,tree object>> which corresponds 85 to the top <<def_directory,directory>> of the stored 86 revision. 87 88[[def_core_git]]core git:: 89 Fundamental data structures and utilities of git. Exposes only limited 90 source code management tools. 91 92[[def_DAG]]DAG:: 93 Directed acyclic graph. The <<def_commit,commit>> objects form a 94 directed acyclic graph, because they have parents (directed), and the 95 graph of commit objects is acyclic (there is no 96 <<def_chain,chain>> which begins and ends with the same 97 <<def_object,object>>). 98 99[[def_dangling_object]]dangling object:: 100 An <<def_unreachable_object,unreachable object>> which is not 101 <<def_reachable,reachable>> even from other unreachable objects; a 102 dangling object has no references to it from any 103 reference or <<def_object,object>> in the <<def_repository,repository>>. 104 105[[def_detached_HEAD]]detached HEAD:: 106 Normally the <<def_HEAD,HEAD>> stores the name of a 107 <<def_branch,branch>>. However, git also allows you to <<def_checkout,check out>> 108 an arbitrary <<def_commit,commit>> that isn't necessarily the tip of any 109 particular branch. In this case HEAD is said to be "detached". 110 111[[def_dircache]]dircache:: 112 You are *waaaaay* behind. See <<def_index,index>>. 113 114[[def_directory]]directory:: 115 The list you get with "ls" :-) 116 117[[def_dirty]]dirty:: 118 A <<def_working_tree,working tree>> is said to be "dirty" if 119 it contains modifications which have not been <<def_commit,committed>> to the current 120 <<def_branch,branch>>. 121 122[[def_ent]]ent:: 123 Favorite synonym to "<<def_tree-ish,tree-ish>>" by some total geeks. See 124 `http://en.wikipedia.org/wiki/Ent_(Middle-earth)` for an in-depth 125 explanation. Avoid this term, not to confuse people. 126 127[[def_evil_merge]]evil merge:: 128 An evil merge is a <<def_merge,merge>> that introduces changes that 129 do not appear in any <<def_parent,parent>>. 130 131[[def_fast_forward]]fast forward:: 132 A fast-forward is a special type of <<def_merge,merge>> where you have a 133 <<def_revision,revision>> and you are "merging" another 134 <<def_branch,branch>>'s changes that happen to be a descendant of what 135 you have. In such these cases, you do not make a new <<def_merge,merge>> 136 <<def_commit,commit>> but instead just update to his 137 revision. This will happen frequently on a 138 <<def_tracking_branch,tracking branch>> of a remote 139 <<def_repository,repository>>. 140 141[[def_fetch]]fetch:: 142 Fetching a <<def_branch,branch>> means to get the 143 branch's <<def_head_ref,head ref>> from a remote 144 <<def_repository,repository>>, to find out which objects are 145 missing from the local <<def_object_database,object database>>, 146 and to get them, too. See also linkgit:git-fetch[1]. 147 148[[def_file_system]]file system:: 149 Linus Torvalds originally designed git to be a user space file system, 150 i.e. the infrastructure to hold files and directories. That ensured the 151 efficiency and speed of git. 152 153[[def_git_archive]]git archive:: 154 Synonym for <<def_repository,repository>> (for arch people). 155 156[[def_grafts]]grafts:: 157 Grafts enables two otherwise different lines of development to be joined 158 together by recording fake ancestry information for commits. This way 159 you can make git pretend the set of <<def_parent,parents>> a <<def_commit,commit>> has 160 is different from what was recorded when the commit was 161 created. Configured via the `.git/info/grafts` file. 162 163[[def_hash]]hash:: 164 In git's context, synonym to <<def_object_name,object name>>. 165 166[[def_head]]head:: 167 A <<def_ref,named reference>> to the <<def_commit,commit>> at the tip of a 168 <<def_branch,branch>>. Heads are stored in 169 `$GIT_DIR/refs/heads/`, except when using packed refs. (See 170 linkgit:git-pack-refs[1].) 171 172[[def_HEAD]]HEAD:: 173 The current <<def_branch,branch>>. In more detail: Your <<def_working_tree, 174 working tree>> is normally derived from the state of the tree 175 referred to by HEAD. HEAD is a reference to one of the 176 <<def_head,heads>> in your repository, except when using a 177 <<def_detached_HEAD,detached HEAD>>, in which case it may 178 reference an arbitrary commit. 179 180[[def_head_ref]]head ref:: 181 A synonym for <<def_head,head>>. 182 183[[def_hook]]hook:: 184 During the normal execution of several git commands, call-outs are made 185 to optional scripts that allow a developer to add functionality or 186 checking. Typically, the hooks allow for a command to be pre-verified 187 and potentially aborted, and allow for a post-notification after the 188 operation is done. The hook scripts are found in the 189 `$GIT_DIR/hooks/` directory, and are enabled by simply 190 making them executable. 191 192[[def_index]]index:: 193 A collection of files with stat information, whose contents are stored 194 as objects. The index is a stored version of your 195 <<def_working_tree,working tree>>. Truth be told, it can also contain a second, and even 196 a third version of a working tree, which are used 197 when <<def_merge,merging>>. 198 199[[def_index_entry]]index entry:: 200 The information regarding a particular file, stored in the 201 <<def_index,index>>. An index entry can be unmerged, if a 202 <<def_merge,merge>> was started, but not yet finished (i.e. if 203 the index contains multiple versions of that file). 204 205[[def_master]]master:: 206 The default development <<def_branch,branch>>. Whenever you 207 create a git <<def_repository,repository>>, a branch named 208 "master" is created, and becomes the active branch. In most 209 cases, this contains the local development, though that is 210 purely by convention and is not required. 211 212[[def_merge]]merge:: 213 As a verb: To bring the contents of another 214 <<def_branch,branch>> (possibly from an external 215 <<def_repository,repository>>) into the current branch. In the 216 case where the merged-in branch is from a different repository, 217 this is done by first <<def_fetch,fetching>> the remote branch 218 and then merging the result into the current branch. This 219 combination of fetch and merge operations is called a 220 <<def_pull,pull>>. Merging is performed by an automatic process 221 that identifies changes made since the branches diverged, and 222 then applies all those changes together. In cases where changes 223 conflict, manual intervention may be required to complete the 224 merge. 225+ 226As a noun: unless it is a <<def_fast_forward,fast forward>>, a 227successful merge results in the creation of a new <<def_commit,commit>> 228representing the result of the merge, and having as 229<<def_parent,parents>> the tips of the merged <<def_branch,branches>>. 230This commit is referred to as a "merge commit", or sometimes just a 231"merge". 232 233[[def_object]]object:: 234 The unit of storage in git. It is uniquely identified by the 235 <<def_SHA1,SHA1>> of its contents. Consequently, an 236 object can not be changed. 237 238[[def_object_database]]object database:: 239 Stores a set of "objects", and an individual <<def_object,object>> is 240 identified by its <<def_object_name,object name>>. The objects usually 241 live in `$GIT_DIR/objects/`. 242 243[[def_object_identifier]]object identifier:: 244 Synonym for <<def_object_name,object name>>. 245 246[[def_object_name]]object name:: 247 The unique identifier of an <<def_object,object>>. The <<def_hash,hash>> 248 of the object's contents using the Secure Hash Algorithm 249 1 and usually represented by the 40 character hexadecimal encoding of 250 the <<def_hash,hash>> of the object. 251 252[[def_object_type]]object type:: 253 One of the identifiers 254 "<<def_commit,commit>>","<<def_tree,tree>>","<<def_tag,tag>>" or "<<def_blob_object,blob>>" 255 describing the type of an <<def_object,object>>. 256 257[[def_octopus]]octopus:: 258 To <<def_merge,merge>> more than two <<def_branch,branches>>. Also denotes an 259 intelligent predator. 260 261[[def_origin]]origin:: 262 The default upstream <<def_repository,repository>>. Most projects have 263 at least one upstream project which they track. By default 264 'origin' is used for that purpose. New upstream updates 265 will be fetched into remote <<def_tracking_branch,tracking branches>> named 266 origin/name-of-upstream-branch, which you can see using 267 "`git branch -r`". 268 269[[def_pack]]pack:: 270 A set of objects which have been compressed into one file (to save space 271 or to transmit them efficiently). 272 273[[def_pack_index]]pack index:: 274 The list of identifiers, and other information, of the objects in a 275 <<def_pack,pack>>, to assist in efficiently accessing the contents of a 276 pack. 277 278[[def_parent]]parent:: 279 A <<def_commit_object,commit object>> contains a (possibly empty) list 280 of the logical predecessor(s) in the line of development, i.e. its 281 parents. 282 283[[def_pickaxe]]pickaxe:: 284 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore 285 routines that help select changes that add or delete a given text 286 string. With the `--pickaxe-all` option, it can be used to view the full 287 <<def_changeset,changeset>> that introduced or removed, say, a 288 particular line of text. See linkgit:git-diff[1]. 289 290[[def_plumbing]]plumbing:: 291 Cute name for <<def_core_git,core git>>. 292 293[[def_porcelain]]porcelain:: 294 Cute name for programs and program suites depending on 295 <<def_core_git,core git>>, presenting a high level access to 296 core git. Porcelains expose more of a <<def_SCM,SCM>> 297 interface than the <<def_plumbing,plumbing>>. 298 299[[def_pull]]pull:: 300 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and 301 <<def_merge,merge>> it. See also linkgit:git-pull[1]. 302 303[[def_push]]push:: 304 Pushing a <<def_branch,branch>> means to get the branch's 305 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>, 306 find out if it is a direct ancestor to the branch's local 307 head ref, and in that case, putting all 308 objects, which are <<def_reachable,reachable>> from the local 309 head ref, and which are missing from the remote 310 repository, into the remote 311 <<def_object_database,object database>>, and updating the remote 312 head ref. If the remote <<def_head,head>> is not an 313 ancestor to the local head, the push fails. 314 315[[def_reachable]]reachable:: 316 All of the ancestors of a given <<def_commit,commit>> are said to be 317 "reachable" from that commit. More 318 generally, one <<def_object,object>> is reachable from 319 another if we can reach the one from the other by a <<def_chain,chain>> 320 that follows <<def_tag,tags>> to whatever they tag, 321 <<def_commit_object,commits>> to their parents or trees, and 322 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>> 323 that they contain. 324 325[[def_rebase]]rebase:: 326 To reapply a series of changes from a <<def_branch,branch>> to a 327 different base, and reset the <<def_head,head>> of that branch 328 to the result. 329 330[[def_ref]]ref:: 331 A 40-byte hex representation of a <<def_SHA1,SHA1>> or a name that 332 denotes a particular <<def_object,object>>. These may be stored in 333 `$GIT_DIR/refs/`. 334 335[[def_reflog]]reflog:: 336 A reflog shows the local "history" of a ref. In other words, 337 it can tell you what the 3rd last revision in _this_ repository 338 was, and what was the current state in _this_ repository, 339 yesterday 9:14pm. See linkgit:git-reflog[1] for details. 340 341[[def_refspec]]refspec:: 342 A "refspec" is used by <<def_fetch,fetch>> and 343 <<def_push,push>> to describe the mapping between remote 344 <<def_ref,ref>> and local ref. They are combined with a colon in 345 the format <src>:<dst>, preceded by an optional plus sign, +. 346 For example: `git fetch $URL 347 refs/heads/master:refs/heads/origin` means "grab the master 348 <<def_branch,branch>> <<def_head,head>> from the $URL and store 349 it as my origin branch head". And `git push 350 $URL refs/heads/master:refs/heads/to-upstream` means "publish my 351 master branch head as to-upstream branch at $URL". See also 352 linkgit:git-push[1]. 353 354[[def_repository]]repository:: 355 A collection of <<def_ref,refs>> together with an 356 <<def_object_database,object database>> containing all objects 357 which are <<def_reachable,reachable>> from the refs, possibly 358 accompanied by meta data from one or more <<def_porcelain,porcelains>>. A 359 repository can share an object database with other repositories 360 via <<def_alternate_object_database,alternates mechanism>>. 361 362[[def_resolve]]resolve:: 363 The action of fixing up manually what a failed automatic 364 <<def_merge,merge>> left behind. 365 366[[def_revision]]revision:: 367 A particular state of files and directories which was stored in the 368 <<def_object_database,object database>>. It is referenced by a 369 <<def_commit_object,commit object>>. 370 371[[def_rewind]]rewind:: 372 To throw away part of the development, i.e. to assign the 373 <<def_head,head>> to an earlier <<def_revision,revision>>. 374 375[[def_SCM]]SCM:: 376 Source code management (tool). 377 378[[def_SHA1]]SHA1:: 379 Synonym for <<def_object_name,object name>>. 380 381[[def_shallow_repository]]shallow repository:: 382 A shallow <<def_repository,repository>> has an incomplete 383 history some of whose <<def_commit,commits>> have <<def_parent,parents>> cauterized away (in other 384 words, git is told to pretend that these commits do not have the 385 parents, even though they are recorded in the <<def_commit_object,commit 386 object>>). This is sometimes useful when you are interested only in the 387 recent history of a project even though the real history recorded in the 388 upstream is much larger. A shallow repository 389 is created by giving the `--depth` option to linkgit:git-clone[1], and 390 its history can be later deepened with linkgit:git-fetch[1]. 391 392[[def_symref]]symref:: 393 Symbolic reference: instead of containing the <<def_SHA1,SHA1>> 394 id itself, it is of the format 'ref: refs/some/thing' and when 395 referenced, it recursively dereferences to this reference. 396 '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic 397 references are manipulated with the linkgit:git-symbolic-ref[1] 398 command. 399 400[[def_tag]]tag:: 401 A <<def_ref,ref>> pointing to a <<def_tag_object,tag>> or 402 <<def_commit_object,commit object>>. In contrast to a <<def_head,head>>, 403 a tag is not changed by a <<def_commit,commit>>. Tags (not 404 <<def_tag_object,tag objects>>) are stored in `$GIT_DIR/refs/tags/`. A 405 git tag has nothing to do with a Lisp tag (which would be 406 called an <<def_object_type,object type>> in git's context). A 407 tag is most typically used to mark a particular point in the 408 commit ancestry <<def_chain,chain>>. 409 410[[def_tag_object]]tag object:: 411 An <<def_object,object>> containing a <<def_ref,ref>> pointing to 412 another object, which can contain a message just like a 413 <<def_commit_object,commit object>>. It can also contain a (PGP) 414 signature, in which case it is called a "signed tag object". 415 416[[def_topic_branch]]topic branch:: 417 A regular git <<def_branch,branch>> that is used by a developer to 418 identify a conceptual line of development. Since branches are very easy 419 and inexpensive, it is often desirable to have several small branches 420 that each contain very well defined concepts or small incremental yet 421 related changes. 422 423[[def_tracking_branch]]tracking branch:: 424 A regular git <<def_branch,branch>> that is used to follow changes from 425 another <<def_repository,repository>>. A tracking 426 branch should not contain direct modifications or have local commits 427 made to it. A tracking branch can usually be 428 identified as the right-hand-side <<def_ref,ref>> in a Pull: 429 <<def_refspec,refspec>>. 430 431[[def_tree]]tree:: 432 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree 433 object>> together with the dependent <<def_blob_object,blob>> and tree objects 434 (i.e. a stored representation of a working tree). 435 436[[def_tree_object]]tree object:: 437 An <<def_object,object>> containing a list of file names and modes along 438 with refs to the associated blob and/or tree objects. A 439 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>. 440 441[[def_tree-ish]]tree-ish:: 442 A <<def_ref,ref>> pointing to either a <<def_commit_object,commit 443 object>>, a <<def_tree_object,tree object>>, or a <<def_tag_object,tag 444 object>> pointing to a tag or commit or tree object. 445 446[[def_unmerged_index]]unmerged index:: 447 An <<def_index,index>> which contains unmerged 448 <<def_index_entry,index entries>>. 449 450[[def_unreachable_object]]unreachable object:: 451 An <<def_object,object>> which is not <<def_reachable,reachable>> from a 452 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference. 453 454[[def_working_tree]]working tree:: 455 The tree of actual checked out files. The working tree is 456 normally equal to the <<def_HEAD,HEAD>> plus any local changes 457 that you have made but not yet committed.