Documentation/glossary.txt

   1 object::
   2         The unit of storage in git. It is uniquely identified by
   3         the SHA1 of its contents. Consequently, an object can not
   4         be changed.
   5
   6 object name::
   7         The unique identifier of an object. The hash of the object's contents
   8         using the Secure Hash Algorithm 1 and usually represented by the 40
   9         character hexadecimal encoding of the hash of the object (possibly
  10         followed by a white space).
  11
  12 SHA1::
  13         Synonym for object name.
  14
  15 object identifier::
  16         Synonym for object name.
  17
  18 hash::
  19         In git's context, synonym to object name.
  20
  21 object database::
  22         Stores a set of "objects", and an individial object is identified
  23         by its object name. The object usually live in $GIT_DIR/objects/.
  24
  25 blob object::
  26         Untyped object, e.g. the contents of a file.
  27
  28 tree object::
  29         An object containing a list of file names and modes along with refs
  30         to the associated blob and/or tree objects. A tree is equivalent
  31         to a directory.
  32
  33 tree::
  34         Either a working tree, or a tree object together with the
  35         dependent blob and tree objects (i.e. a stored representation
  36         of a working tree).
  37
  38 DAG::
  39         Directed acyclic graph. The commit objects form a directed acyclic
  40         graph, because they have parents (directed), and the graph of commit
  41         objects is acyclic (there is no chain which begins and ends with the
  42         same object).
  43
  44 index::
  45         A collection of files with stat information, whose contents are
  46         stored as objects. The index is a stored version of your working
  47         tree. Truth be told, it can also contain a second, and even a third
  48         version of a working tree, which are used when merging.
  49
  50 index entry::
  51         The information regarding a particular file, stored in the index.
  52         An index entry can be unmerged, if a merge was started, but not
  53         yet finished (i.e. if the index contains multiple versions of
  54         that file).
  55
  56 unmerged index:
  57         An index which contains unmerged index entries.
  58
  59 cache::
  60         Obsolete for: index.
  61
  62 working tree::
  63         The set of files and directories currently being worked on,
  64         i.e. you can work in your working tree without using git at all.
  65
  66 directory::
  67         The list you get with "ls" :-)
  68
  69 revision::
  70         A particular state of files and directories which was stored in
  71         the object database. It is referenced by a commit object.
  72
  73 checkout::
  74         The action of updating the working tree to a revision which was
  75         stored in the object database.
  76
  77 commit::
  78         As a verb: The action of storing the current state of the index in the
  79         object database. The result is a revision.
  80         As a noun: Short hand for commit object.
  81
  82 commit object::
  83         An object which contains the information about a particular
  84         revision, such as parents, committer, author, date and the
  85         tree object which corresponds to the top directory of the
  86         stored revision.
  87
  88 parent::
  89         A commit object contains a (possibly empty) list of the logical
  90         predecessor(s) in the line of development, i.e. its parents.
  91
  92 changeset::
  93         BitKeeper/cvsps speak for "commit". Since git does not store
  94         changes, but states, it really does not make sense to use
  95         the term "changesets" with git.
  96
  97 clean::
  98         A working tree is clean, if it corresponds to the revision
  99         referenced by the current head.
 100
 101 dirty::
 102         A working tree is said to be dirty if it contains modifications
 103         which have not been committed to the current branch.
 104
 105 head::
 106         The top of a branch. It contains a ref to the corresponding
 107         commit object.
 108
 109 branch::
 110         A non-cyclical graph of revisions, i.e. the complete history of
 111         a particular revision, which is called the branch head. The
 112         branch heads are stored in $GIT_DIR/refs/heads/.
 113
 114 ref::
 115         A 40-byte hex representation of a SHA1 pointing to a particular
 116         object. These may be stored in $GIT_DIR/refs/.
 117
 118 head ref::
 119         A ref pointing to a head. Often, this is abbreviated to "head".
 120         Head refs are stored in $GIT_DIR/refs/heads/.
 121
 122 tree-ish::
 123         A ref pointing to either a commit object, a tree object, or a
 124         tag object pointing to a tag or commit or tree object.
 125
 126 ent::
 127         Favorite synonym to "tree-ish" by some total geeks. See
 128         http://en.wikipedia.org/wiki/Ent_(Middle-earth) for an in-depth
 129         explanation.
 130
 131 tag object::
 132         An object containing a ref pointing to another object, which can
 133         contain a message just like a commit object. It can also
 134         contain a (PGP) signature, in which case it is called a "signed
 135         tag object".
 136
 137 tag::
 138         A ref pointing to a tag or commit object. In contrast to a head,
 139         a tag is not changed by a commit. Tags (not tag objects) are
 140         stored in $GIT_DIR/refs/tags/. A git tag has nothing to do with
 141         a Lisp tag (which is called object type in git's context).
 142         A tag is most typically used to mark a particular point in the
 143         commit ancestry chain.
 144
 145 merge::
 146         To merge branches means to try to accumulate the changes since a
 147         common ancestor and apply them to the first branch. An automatic
 148         merge uses heuristics to accomplish that. Evidently, an automatic
 149         merge can fail.
 150
 151 octopus::
 152         To merge more than two branches. Also denotes an intelligent
 153         predator.
 154
 155 resolve::
 156         The action of fixing up manually what a failed automatic merge
 157         left behind.
 158
 159 rewind::
 160         To throw away part of the development, i.e. to assign the head to
 161         an earlier revision.
 162
 163 rebase::
 164         To clean a branch by starting from the head of the main line of
 165         development ("master"), and reapply the (possibly cherry-picked)
 166         changes from that branch.
 167
 168 repository::
 169         A collection of refs together with an object database containing
 170         all objects, which are reachable from the refs, possibly accompanied
 171         by meta data from one or more porcelains. A repository can
 172         share an object database with other repositories.
 173
 174 git archive::
 175         Synonym for repository (for arch people).
 176
 177 file system::
 178         Linus Torvalds originally designed git to be a user space file
 179         system, i.e. the infrastructure to hold files and directories.
 180         That ensured the efficiency and speed of git.
 181
 182 alternate object database::
 183         Via the alternates mechanism, a repository can inherit part of its
 184         object database from another object database, which is called
 185         "alternate".
 186
 187 reachable::
 188         An object is reachable from a ref/commit/tree/tag, if there is a
 189         chain leading from the latter to the former.
 190
 191 chain::
 192         A list of objects, where each object in the list contains a
 193         reference to its successor (for example, the successor of a commit
 194         could be one of its parents).
 195
 196 fetch::
 197         Fetching a branch means to get the branch's head ref from a
 198         remote repository, to find out which objects are missing from
 199         the local object database, and to get them, too.
 200
 201 pull::
 202         Pulling a branch means to fetch it and merge it.
 203
 204 push::
 205         Pushing a branch means to get the branch's head ref from a remote
 206         repository, find out if it is an ancestor to the branch's local
 207         head ref is a direct, and in that case, putting all objects, which
 208         are reachable from the local head ref, and which are missing from
 209         the remote repository, into the remote object database, and updating
 210         the remote head ref. If the remote head is not an ancestor to the
 211         local head, the push fails.
 212
 213 pack::
 214         A set of objects which have been compressed into one file (to save
 215         space or to transmit them efficiently).
 216
 217 pack index::
 218         The list of identifiers, and other information, of the objects in a
 219         pack, to assist in efficiently accessing the contents of a pack.
 220
 221 core git::
 222         Fundamental data structures and utilities of git. Exposes only
 223         limited source code management tools.
 224
 225 plumbing::
 226         Cute name for core git.
 227
 228 porcelain::
 229         Cute name for programs and program suites depending on core git,
 230         presenting a high level access to core git. Porcelains expose
 231         more of a SCM interface than the plumbing.
 232
 233 object type:
 234         One of the identifiers "commit","tree","tag" and "blob" describing
 235         the type of an object.
 236
 237 SCM::
 238         Source code management (tool).
 239
 240 dircache::
 241         You are *waaaaay* behind.
 242