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