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