глоссарий Git (A Git Glossary)
Описание (Description)
alternate object database
Via the alternates mechanism, a repository can inherit part
of its object database from another object database, which is
called an "alternate".
bare repository
A bare repository is normally an appropriately named
directory with a .git suffix that does not have a locally
checked-out copy of any of the files under revision control.
That is, all of the Git administrative and control files that
would normally be present in the hidden .git sub-directory
are directly present in the repository.git directory instead,
and no other files are present and checked out. Usually
publishers of public repositories make bare repositories
available.
blob object
Untyped object, e.g. the contents of a file.
branch
A "branch" is a line of development. The most recent commit
on a branch is referred to as the tip of that branch. The tip
of the branch is referenced by a branch head, which moves
forward as additional development is done on the branch. A
single Git repository can track an arbitrary number of
branches, but your working tree is associated with just one
of them (the "current" or "checked out" branch), and HEAD
points to that branch.
cache
Obsolete for: index.
chain
A list of objects, where each object in the list contains a
reference to its successor (for example, the successor of a
commit could be one of its parents).
changeset
BitKeeper/cvsps speak for "commit". Since Git does not store
changes, but states, it really does not make sense to use the
term "changesets" with Git.
checkout
The action of updating all or part of the working tree with a
tree object or blob from the object database, and updating
the index and HEAD if the whole working tree has been pointed
at a new branch.
cherry-picking
In SCM jargon, "cherry pick" means to choose a subset of
changes out of a series of changes (typically commits) and
record them as a new series of changes on top of a different
codebase. In Git, this is performed by the "git cherry-pick"
command to extract the change introduced by an existing
commit and to record it based on the tip of the current
branch as a new commit.
clean
A working tree is clean, if it corresponds to the revision
referenced by the current head. Also see "dirty".
commit
As a noun: A single point in the Git history; the entire
history of a project is represented as a set of interrelated
commits. The word "commit" is often used by Git in the same
places other revision control systems use the words
"revision" or "version". Also used as a short hand for commit
object.
As a verb: The action of storing a new snapshot of the
project's state in the Git history, by creating a new commit
representing the current state of the index and advancing
HEAD to point at the new commit.
commit object
An object which contains the information about a particular
revision, such as parents, committer, author, date and the
tree object which corresponds to the top directory of the
stored revision.
commit-ish (also committish)
A commit object or an object that can be recursively
dereferenced to a commit object. The following are all
commit-ishes: a commit object, a tag object that points to a
commit object, a tag object that points to a tag object that
points to a commit object, etc.
core Git
Fundamental data structures and utilities of Git. Exposes
only limited source code management tools.
DAG
Directed acyclic graph. The commit objects form a directed
acyclic graph, because they have parents (directed), and the
graph of commit objects is acyclic (there is no chain which
begins and ends with the same object).
dangling object
An unreachable object which is not reachable even from other
unreachable objects; a dangling object has no references to
it from any reference or object in the repository.
detached HEAD
Normally the HEAD stores the name of a branch, and commands
that operate on the history HEAD represents operate on the
history leading to the tip of the branch the HEAD points at.
However, Git also allows you to check out an arbitrary commit
that isn't necessarily the tip of any particular branch. The
HEAD in such a state is called "detached".
Note that commands that operate on the history of the current
branch (e.g. git commit to build a new history on top of it)
still work while the HEAD is detached. They update the HEAD
to point at the tip of the updated history without affecting
any branch. Commands that update or inquire information about
the current branch (e.g. git branch --set-upstream-to that
sets what remote-tracking branch the current branch
integrates with) obviously do not work, as there is no (real)
current branch to ask about in this state.
directory
The list you get with "ls" :-)
dirty
A working tree is said to be "dirty" if it contains
modifications which have not been committed to the current
branch.
evil merge
An evil merge is a merge that introduces changes that do not
appear in any parent.
fast-forward
A fast-forward is a special type of merge where you have a
revision and you are "merging" another branch's changes that
happen to be a descendant of what you have. In such a case,
you do not make a new merge commit but instead just update
your branch to point at the same revision as the branch you
are merging. This will happen frequently on a remote-tracking
branch of a remote repository.
fetch
Fetching a branch means to get the branch's head ref from a
remote repository, to find out which objects are missing from
the local object database, and to get them, too. See also
git-fetch(1).
file system
Linus Torvalds originally designed Git to be a user space
file system, i.e. the infrastructure to hold files and
directories. That ensured the efficiency and speed of Git.
Git archive
Synonym for repository (for arch people).
gitfile
A plain file .git at the root of a working tree that points
at the directory that is the real repository.
grafts
Grafts enables two otherwise different lines of development
to be joined together by recording fake ancestry information
for commits. This way you can make Git pretend the set of
parents a commit has is different from what was recorded when
the commit was created. Configured via the .git/info/grafts
file.
Note that the grafts mechanism is outdated and can lead to
problems transferring objects between repositories; see
git-replace(1) for a more flexible and robust system to do
the same thing.
hash
In Git's context, synonym for object name.
head
A named reference to the commit at the tip of a branch. Heads
are stored in a file in $GIT_DIR/refs/heads/ directory,
except when using packed refs. (See git-pack-refs(1).)
HEAD
The current branch. In more detail: Your working tree is
normally derived from the state of the tree referred to by
HEAD. HEAD is a reference to one of the heads in your
repository, except when using a detached HEAD, in which case
it directly references an arbitrary commit.
head ref
A synonym for head.
hook
During the normal execution of several Git commands,
call-outs are made to optional scripts that allow a developer
to add functionality or checking. Typically, the hooks allow
for a command to be pre-verified and potentially aborted, and
allow for a post-notification after the operation is done.
The hook scripts are found in the $GIT_DIR/hooks/ directory,
and are enabled by simply removing the .sample suffix from
the filename. In earlier versions of Git you had to make them
executable.
index
A collection of files with stat information, whose contents
are stored as objects. The index is a stored version of your
working tree. Truth be told, it can also contain a second,
and even a third version of a working tree, which are used
when merging.
index entry
The information regarding a particular file, stored in the
index. An index entry can be unmerged, if a merge was
started, but not yet finished (i.e. if the index contains
multiple versions of that file).
master
The default development branch. Whenever you create a Git
repository, a branch named "master" is created, and becomes
the active branch. In most cases, this contains the local
development, though that is purely by convention and is not
required.
merge
As a verb: To bring the contents of another branch (possibly
from an external repository) into the current branch. In the
case where the merged-in branch is from a different
repository, this is done by first fetching the remote branch
and then merging the result into the current branch. This
combination of fetch and merge operations is called a pull.
Merging is performed by an automatic process that identifies
changes made since the branches diverged, and then applies
all those changes together. In cases where changes conflict,
manual intervention may be required to complete the merge.
As a noun: unless it is a fast-forward, a successful merge
results in the creation of a new commit representing the
result of the merge, and having as parents the tips of the
merged branches. This commit is referred to as a "merge
commit", or sometimes just a "merge".
object
The unit of storage in Git. It is uniquely identified by the
SHA-1 of its contents. Consequently, an object cannot be
changed.
object database
Stores a set of "objects", and an individual object is
identified by its object name. The objects usually live in
$GIT_DIR/objects/.
object identifier
Synonym for object name.
object name
The unique identifier of an object. The object name is
usually represented by a 40 character hexadecimal string.
Also colloquially called SHA-1.
object type
One of the identifiers "commit", "tree", "tag" or "blob"
describing the type of an object.
octopus
To merge more than two branches.
origin
The default upstream repository. Most projects have at least
one upstream project which they track. By default origin is
used for that purpose. New upstream updates will be fetched
into remote-tracking branches named
origin/name-of-upstream-branch, which you can see using git
branch -r.
overlay
Only update and add files to the working directory, but don't
delete them, similar to how cp -R would update the contents
in the destination directory. This is the default mode in a
checkout when checking out files from the index or a
tree-ish. In contrast, no-overlay mode also deletes tracked
files not present in the source, similar to rsync --delete.
pack
A set of objects which have been compressed into one file (to
save space or to transmit them efficiently).
pack index
The list of identifiers, and other information, of the
objects in a pack, to assist in efficiently accessing the
contents of a pack.
pathspec
Pattern used to limit paths in Git commands.
Pathspecs are used on the command line of "git ls-files",
"git ls-tree", "git add", "git grep", "git diff", "git
checkout", and many other commands to limit the scope of
operations to some subset of the tree or worktree. See the
documentation of each command for whether paths are relative
to the current directory or toplevel. The pathspec syntax is
as follows:
• any path matches itself
• the pathspec up to the last slash represents a directory
prefix. The scope of that pathspec is limited to that
subtree.
• the rest of the pathspec is a pattern for the remainder
of the pathname. Paths relative to the directory prefix
will be matched against that pattern using fnmatch(3); in
particular, * and ? can match directory separators.
For example, Documentation/*.jpg will match all .jpg files in
the Documentation subtree, including
Documentation/chapter_1/figure_1.jpg.
A pathspec that begins with a colon : has special meaning. In
the short form, the leading colon : is followed by zero or
more "magic signature" letters (which optionally is
terminated by another colon :), and the remainder is the
pattern to match against the path. The "magic signature"
consists of ASCII symbols that are neither alphanumeric,
glob, regex special characters nor colon. The optional colon
that terminates the "magic signature" can be omitted if the
pattern begins with a character that does not belong to
"magic signature" symbol set and is not a colon.
In the long form, the leading colon : is followed by an open
parenthesis (, a comma-separated list of zero or more "magic
words", and a close parentheses ), and the remainder is the
pattern to match against the path.
A pathspec with only a colon means "there is no pathspec".
This form should not be combined with other pathspec.
top
The magic word top (magic signature: /) makes the pattern
match from the root of the working tree, even when you
are running the command from inside a subdirectory.
literal
Wildcards in the pattern such as * or ? are treated as
literal characters.
icase
Case insensitive match.
glob
Git treats the pattern as a shell glob suitable for
consumption by fnmatch(3) with the FNM_PATHNAME flag:
wildcards in the pattern will not match a / in the
pathname. For example, "Documentation/*.html" matches
"Documentation/git.html" but not
"Documentation/ppc/ppc.html" or
"tools/perf/Documentation/perf.html".
Two consecutive asterisks ("**") in patterns matched
against full pathname may have special meaning:
• A leading "**" followed by a slash means match in all
directories. For example, "**/foo" matches file or
directory "foo" anywhere, the same as pattern "foo".
"**/foo/bar" matches file or directory "bar" anywhere
that is directly under directory "foo".
• A trailing "/**" matches everything inside. For
example, "abc/**" matches all files inside directory
"abc", relative to the location of the .gitignore
file, with infinite depth.
• A slash followed by two consecutive asterisks then a
slash matches zero or more directories. For example,
"a/**/b" matches "a/b", "a/x/b", "a/x/y/b" and so on.
• Other consecutive asterisks are considered invalid.
Glob magic is incompatible with literal magic.
attr
After attr: comes a space separated list of "attribute
requirements", all of which must be met in order for the
path to be considered a match; this is in addition to the
usual non-magic pathspec pattern matching. See
gitattributes(5).
Each of the attribute requirements for the path takes one
of these forms:
• "ATTR" requires that the attribute ATTR be set.
• "-ATTR" requires that the attribute ATTR be unset.
• "ATTR=VALUE" requires that the attribute ATTR be set
to the string VALUE.
• "!ATTR" requires that the attribute ATTR be
unspecified.
Note that when matching against a tree object,
attributes are still obtained from working tree, not
from the given tree object.
exclude
After a path matches any non-exclude pathspec, it will be
run through all exclude pathspecs (magic signature: ! or
its synonym ^). If it matches, the path is ignored. When
there is no non-exclude pathspec, the exclusion is
applied to the result set as if invoked without any
pathspec.
parent
A commit object contains a (possibly empty) list of the
logical predecessor(s) in the line of development, i.e. its
parents.
pickaxe
The term pickaxe refers to an option to the diffcore routines
that help select changes that add or delete a given text
string. With the --pickaxe-all option, it can be used to view
the full changeset that introduced or removed, say, a
particular line of text. See git-diff(1).
plumbing
Cute name for core Git.
porcelain
Cute name for programs and program suites depending on core
Git, presenting a high level access to core Git. Porcelains
expose more of a SCM interface than the plumbing.
per-worktree ref
Refs that are per-worktree, rather than global. This is
presently only HEAD and any refs that start with
refs/bisect/, but might later include other unusual refs.
pseudoref
Pseudorefs are a class of files under $GIT_DIR which behave
like refs for the purposes of rev-parse, but which are
treated specially by git. Pseudorefs both have names that are
all-caps, and always start with a line consisting of a SHA-1
followed by whitespace. So, HEAD is not a pseudoref, because
it is sometimes a symbolic ref. They might optionally contain
some additional data. MERGE_HEAD and CHERRY_PICK_HEAD are
examples. Unlike per-worktree refs, these files cannot be
symbolic refs, and never have reflogs. They also cannot be
updated through the normal ref update machinery. Instead,
they are updated by directly writing to the files. However,
they can be read as if they were refs, so git rev-parse
MERGE_HEAD will work.
pull
Pulling a branch means to fetch it and merge it. See also
git-pull(1).
push
Pushing a branch means to get the branch's head ref from a
remote repository, find out if it is an ancestor to the
branch's local head ref, and in that case, putting all
objects, which are reachable from the local head ref, and
which are missing from the remote repository, into the remote
object database, and updating the remote head ref. If the
remote head is not an ancestor to the local head, the push
fails.
reachable
All of the ancestors of a given commit are said to be
"reachable" from that commit. More generally, one object is
reachable from another if we can reach the one from the other
by a chain that follows tags to whatever they tag, commits to
their parents or trees, and trees to the trees or blobs that
they contain.
rebase
To reapply a series of changes from a branch to a different
base, and reset the head of that branch to the result.
ref
A name that begins with refs/ (e.g. refs/heads/master) that
points to an object name or another ref (the latter is called
a symbolic ref). For convenience, a ref can sometimes be
abbreviated when used as an argument to a Git command; see
gitrevisions(7) for details. Refs are stored in the
repository.
The ref namespace is hierarchical. Different subhierarchies
are used for different purposes (e.g. the refs/heads/
hierarchy is used to represent local branches).
There are a few special-purpose refs that do not begin with
refs/. The most notable example is HEAD.
reflog
A reflog shows the local "history" of a ref. In other words,
it can tell you what the 3rd last revision in this repository
was, and what was the current state in this repository,
yesterday 9:14pm. See git-reflog(1) for details.
refspec
A "refspec" is used by fetch and push to describe the mapping
between remote ref and local ref.
remote repository
A repository which is used to track the same project but
resides somewhere else. To communicate with remotes, see
fetch or push.
remote-tracking branch
A ref that is used to follow changes from another repository.
It typically looks like refs/remotes/foo/bar (indicating that
it tracks a branch named bar in a remote named foo), and
matches the right-hand-side of a configured fetch refspec. A
remote-tracking branch should not contain direct
modifications or have local commits made to it.
repository
A collection of refs together with an object database
containing all objects which are reachable from the refs,
possibly accompanied by meta data from one or more
porcelains. A repository can share an object database with
other repositories via alternates mechanism.
resolve
The action of fixing up manually what a failed automatic
merge left behind.
revision
Synonym for commit (the noun).
rewind
To throw away part of the development, i.e. to assign the
head to an earlier revision.
SCM
Source code management (tool).
SHA-1
"Secure Hash Algorithm 1"; a cryptographic hash function. In
the context of Git used as a synonym for object name.
shallow clone
Mostly a synonym to shallow repository but the phrase makes
it more explicit that it was created by running git clone
--depth=... command.
shallow repository
A shallow repository has an incomplete history some of whose
commits have parents cauterized away (in other words, Git is
told to pretend that these commits do not have the parents,
even though they are recorded in the commit object). This is
sometimes useful when you are interested only in the recent
history of a project even though the real history recorded in
the upstream is much larger. A shallow repository is created
by giving the --depth option to git-clone(1), and its history
can be later deepened with git-fetch(1).
stash entry
An object used to temporarily store the contents of a dirty
working directory and the index for future reuse.
submodule
A repository that holds the history of a separate project
inside another repository (the latter of which is called
superproject).
superproject
A repository that references repositories of other projects
in its working tree as submodules. The superproject knows
about the names of (but does not hold copies of) commit
objects of the contained submodules.
symref
Symbolic reference: instead of containing the SHA-1 id
itself, it is of the format ref: refs/some/thing and when
referenced, it recursively dereferences to this reference.
HEAD is a prime example of a symref. Symbolic references are
manipulated with the git-symbolic-ref(1) command.
tag
A ref under refs/tags/ namespace that points to an object of
an arbitrary type (typically a tag points to either a tag or
a commit object). In contrast to a head, a tag is not updated
by the commit command. A Git tag has nothing to do with a
Lisp tag (which would be called an object type in Git's
context). A tag is most typically used to mark a particular
point in the commit ancestry chain.
tag object
An object containing a ref pointing to another object, which
can contain a message just like a commit object. It can also
contain a (PGP) signature, in which case it is called a
"signed tag object".
topic branch
A regular Git branch that is used by a developer to identify
a conceptual line of development. Since branches are very
easy and inexpensive, it is often desirable to have several
small branches that each contain very well defined concepts
or small incremental yet related changes.
tree
Either a working tree, or a tree object together with the
dependent blob and tree objects (i.e. a stored representation
of a working tree).
tree object
An object containing a list of file names and modes along
with refs to the associated blob and/or tree objects. A tree
is equivalent to a directory.
tree-ish (also treeish)
A tree object or an object that can be recursively
dereferenced to a tree object. Dereferencing a commit object
yields the tree object corresponding to the revision's top
directory. The following are all tree-ishes: a commit-ish, a
tree object, a tag object that points to a tree object, a tag
object that points to a tag object that points to a tree
object, etc.
unmerged index
An index which contains unmerged index entries.
unreachable object
An object which is not reachable from a branch, tag, or any
other reference.
upstream branch
The default branch that is merged into the branch in question
(or the branch in question is rebased onto). It is configured
via branch.<name>.remote and branch.<name>.merge. If the
upstream branch of A is origin/B sometimes we say "A is
tracking origin/B".
working tree
The tree of actual checked out files. The working tree
normally contains the contents of the HEAD commit's tree,
plus any local changes that you have made but not yet
committed.
