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 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_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 linkgit: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 `$GIT_DIR/refs/heads/`, except when using packed refs. (See 167 linkgit:git-pack-refs[1].) 168 169[[def_HEAD]]HEAD:: 170 The current <<def_branch,branch>>. In more detail: Your <<def_working_tree, 171 working tree>> is normally derived from the state of the tree 172 referred to by HEAD. HEAD is a reference to one of the 173 <<def_head,heads>> in your repository, except when using a 174 <<def_detached_HEAD,detached HEAD>>, in which case it may 175 reference an arbitrary commit. 176 177[[def_head_ref]]head ref:: 178 A synonym for <<def_head,head>>. 179 180[[def_hook]]hook:: 181 During the normal execution of several git commands, call-outs are made 182 to optional scripts that allow a developer to add functionality or 183 checking. Typically, the hooks allow for a command to be pre-verified 184 and potentially aborted, and allow for a post-notification after the 185 operation is done. The hook scripts are found in the 186 `$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. 248 249[[def_object_type]]object type:: 250 One of the identifiers 251 "<<def_commit,commit>>","<<def_tree,tree>>","<<def_tag,tag>>" or "<<def_blob_object,blob>>" 252 describing the type of an <<def_object,object>>. 253 254[[def_octopus]]octopus:: 255 To <<def_merge,merge>> more than two <<def_branch,branches>>. Also denotes an 256 intelligent predator. 257 258[[def_origin]]origin:: 259 The default upstream <<def_repository,repository>>. Most projects have 260 at least one upstream project which they track. By default 261 'origin' is used for that purpose. New upstream updates 262 will be fetched into remote <<def_tracking_branch,tracking branches>> named 263 origin/name-of-upstream-branch, which you can see using 264 "`git branch -r`". 265 266[[def_pack]]pack:: 267 A set of objects which have been compressed into one file (to save space 268 or to transmit them efficiently). 269 270[[def_pack_index]]pack index:: 271 The list of identifiers, and other information, of the objects in a 272 <<def_pack,pack>>, to assist in efficiently accessing the contents of a 273 pack. 274 275[[def_parent]]parent:: 276 A <<def_commit_object,commit object>> contains a (possibly empty) list 277 of the logical predecessor(s) in the line of development, i.e. its 278 parents. 279 280[[def_pickaxe]]pickaxe:: 281 The term <<def_pickaxe,pickaxe>> refers to an option to the diffcore 282 routines that help select changes that add or delete a given text 283 string. With the `--pickaxe-all` option, it can be used to view the full 284 <<def_changeset,changeset>> that introduced or removed, say, a 285 particular line of text. See linkgit:git-diff[1]. 286 287[[def_plumbing]]plumbing:: 288 Cute name for <<def_core_git,core git>>. 289 290[[def_porcelain]]porcelain:: 291 Cute name for programs and program suites depending on 292 <<def_core_git,core git>>, presenting a high level access to 293 core git. Porcelains expose more of a <<def_SCM,SCM>> 294 interface than the <<def_plumbing,plumbing>>. 295 296[[def_pull]]pull:: 297 Pulling a <<def_branch,branch>> means to <<def_fetch,fetch>> it and 298 <<def_merge,merge>> it. See also linkgit:git-pull[1]. 299 300[[def_push]]push:: 301 Pushing a <<def_branch,branch>> means to get the branch's 302 <<def_head_ref,head ref>> from a remote <<def_repository,repository>>, 303 find out if it is a direct ancestor to the branch's local 304 head ref, and in that case, putting all 305 objects, which are <<def_reachable,reachable>> from the local 306 head ref, and which are missing from the remote 307 repository, into the remote 308 <<def_object_database,object database>>, and updating the remote 309 head ref. If the remote <<def_head,head>> is not an 310 ancestor to the local head, the push fails. 311 312[[def_reachable]]reachable:: 313 All of the ancestors of a given <<def_commit,commit>> are said to be 314 "reachable" from that commit. More 315 generally, one <<def_object,object>> is reachable from 316 another if we can reach the one from the other by a <<def_chain,chain>> 317 that follows <<def_tag,tags>> to whatever they tag, 318 <<def_commit_object,commits>> to their parents or trees, and 319 <<def_tree_object,trees>> to the trees or <<def_blob_object,blobs>> 320 that they contain. 321 322[[def_rebase]]rebase:: 323 To reapply a series of changes from a <<def_branch,branch>> to a 324 different base, and reset the <<def_head,head>> of that branch 325 to the result. 326 327[[def_ref]]ref:: 328 A 40-byte hex representation of a <<def_SHA1,SHA1>> or a name that 329 denotes a particular <<def_object,object>>. These may be stored in 330 `$GIT_DIR/refs/`. 331 332[[def_reflog]]reflog:: 333 A reflog shows the local "history" of a ref. In other words, 334 it can tell you what the 3rd last revision in _this_ repository 335 was, and what was the current state in _this_ repository, 336 yesterday 9:14pm. See linkgit:git-reflog[1] for details. 337 338[[def_refspec]]refspec:: 339 A "refspec" is used by <<def_fetch,fetch>> and 340 <<def_push,push>> to describe the mapping between remote 341 <<def_ref,ref>> and local ref. They are combined with a colon in 342 the format <src>:<dst>, preceded by an optional plus sign, +. 343 For example: `git fetch $URL 344 refs/heads/master:refs/heads/origin` means "grab the master 345 <<def_branch,branch>> <<def_head,head>> from the $URL and store 346 it as my origin branch head". And `git push 347 $URL refs/heads/master:refs/heads/to-upstream` means "publish my 348 master branch head as to-upstream branch at $URL". See also 349 linkgit:git-push[1]. 350 351[[def_repository]]repository:: 352 A collection of <<def_ref,refs>> together with an 353 <<def_object_database,object database>> containing all objects 354 which are <<def_reachable,reachable>> from the refs, possibly 355 accompanied by meta data from one or more <<def_porcelain,porcelains>>. A 356 repository can share an object database with other repositories 357 via <<def_alternate_object_database,alternates mechanism>>. 358 359[[def_resolve]]resolve:: 360 The action of fixing up manually what a failed automatic 361 <<def_merge,merge>> left behind. 362 363[[def_revision]]revision:: 364 A particular state of files and directories which was stored in the 365 <<def_object_database,object database>>. It is referenced by a 366 <<def_commit_object,commit object>>. 367 368[[def_rewind]]rewind:: 369 To throw away part of the development, i.e. to assign the 370 <<def_head,head>> to an earlier <<def_revision,revision>>. 371 372[[def_SCM]]SCM:: 373 Source code management (tool). 374 375[[def_SHA1]]SHA1:: 376 Synonym for <<def_object_name,object name>>. 377 378[[def_shallow_repository]]shallow repository:: 379 A shallow <<def_repository,repository>> has an incomplete 380 history some of whose <<def_commit,commits>> have <<def_parent,parents>> cauterized away (in other 381 words, git is told to pretend that these commits do not have the 382 parents, even though they are recorded in the <<def_commit_object,commit 383 object>>). This is sometimes useful when you are interested only in the 384 recent history of a project even though the real history recorded in the 385 upstream is much larger. A shallow repository 386 is created by giving the `--depth` option to linkgit:git-clone[1], and 387 its history can be later deepened with linkgit:git-fetch[1]. 388 389[[def_symref]]symref:: 390 Symbolic reference: instead of containing the <<def_SHA1,SHA1>> 391 id itself, it is of the format 'ref: refs/some/thing' and when 392 referenced, it recursively dereferences to this reference. 393 '<<def_HEAD,HEAD>>' is a prime example of a symref. Symbolic 394 references are manipulated with the linkgit:git-symbolic-ref[1] 395 command. 396 397[[def_tag]]tag:: 398 A <<def_ref,ref>> pointing to a <<def_tag_object,tag>> or 399 <<def_commit_object,commit object>>. In contrast to a <<def_head,head>>, 400 a tag is not changed by a <<def_commit,commit>>. Tags (not 401 <<def_tag_object,tag objects>>) are stored in `$GIT_DIR/refs/tags/`. A 402 git tag has nothing to do with a Lisp tag (which would be 403 called an <<def_object_type,object type>> in git's context). A 404 tag is most typically used to mark a particular point in the 405 commit ancestry <<def_chain,chain>>. 406 407[[def_tag_object]]tag object:: 408 An <<def_object,object>> containing a <<def_ref,ref>> pointing to 409 another object, which can contain a message just like a 410 <<def_commit_object,commit object>>. It can also contain a (PGP) 411 signature, in which case it is called a "signed tag object". 412 413[[def_topic_branch]]topic branch:: 414 A regular git <<def_branch,branch>> that is used by a developer to 415 identify a conceptual line of development. Since branches are very easy 416 and inexpensive, it is often desirable to have several small branches 417 that each contain very well defined concepts or small incremental yet 418 related changes. 419 420[[def_tracking_branch]]tracking branch:: 421 A regular git <<def_branch,branch>> that is used to follow changes from 422 another <<def_repository,repository>>. A tracking 423 branch should not contain direct modifications or have local commits 424 made to it. A tracking branch can usually be 425 identified as the right-hand-side <<def_ref,ref>> in a Pull: 426 <<def_refspec,refspec>>. 427 428[[def_tree]]tree:: 429 Either a <<def_working_tree,working tree>>, or a <<def_tree_object,tree 430 object>> together with the dependent <<def_blob_object,blob>> and tree objects 431 (i.e. a stored representation of a working tree). 432 433[[def_tree_object]]tree object:: 434 An <<def_object,object>> containing a list of file names and modes along 435 with refs to the associated blob and/or tree objects. A 436 <<def_tree,tree>> is equivalent to a <<def_directory,directory>>. 437 438[[def_tree-ish]]tree-ish:: 439 A <<def_ref,ref>> pointing to either a <<def_commit_object,commit 440 object>>, a <<def_tree_object,tree object>>, or a <<def_tag_object,tag 441 object>> pointing to a tag or commit or tree object. 442 443[[def_unmerged_index]]unmerged index:: 444 An <<def_index,index>> which contains unmerged 445 <<def_index_entry,index entries>>. 446 447[[def_unreachable_object]]unreachable object:: 448 An <<def_object,object>> which is not <<def_reachable,reachable>> from a 449 <<def_branch,branch>>, <<def_tag,tag>>, or any other reference. 450 451[[def_working_tree]]working tree:: 452 The tree of actual checked out files. The working tree is 453 normally equal to the <<def_HEAD,HEAD>> plus any local changes 454 that you have made but not yet committed.