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