1GITSUBMODULES(7)                  Git Manual                  GITSUBMODULES(7)
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NAME

6       gitsubmodules - Mounting one repository inside another
7

SYNOPSIS

9       .gitmodules, $GIT_DIR/config
10
11       git submodule
12       git <command> --recurse-submodules
13

DESCRIPTION

15       A submodule is a repository embedded inside another repository. The
16       submodule has its own history; the repository it is embedded in is
17       called a superproject.
18
19       On the filesystem, a submodule usually (but not always - see FORMS
20       below) consists of (i) a Git directory located under the
21       $GIT_DIR/modules/ directory of its superproject, (ii) a working
22       directory inside the superproject’s working directory, and a .git file
23       at the root of the submodule’s working directory pointing to (i).
24
25       Assuming the submodule has a Git directory at $GIT_DIR/modules/foo/ and
26       a working directory at path/to/bar/, the superproject tracks the
27       submodule via a gitlink entry in the tree at path/to/bar and an entry
28       in its .gitmodules file (see gitmodules(5)) of the form
29       submodule.foo.path = path/to/bar.
30
31       The gitlink entry contains the object name of the commit that the
32       superproject expects the submodule’s working directory to be at.
33
34       The section submodule.foo.* in the .gitmodules file gives additional
35       hints to Git’s porcelain layer. For example, the submodule.foo.url
36       setting specifies where to obtain the submodule.
37
38       Submodules can be used for at least two different use cases:
39
40        1. Using another project while maintaining independent history.
41           Submodules allow you to contain the working tree of another project
42           within your own working tree while keeping the history of both
43           projects separate. Also, since submodules are fixed to an arbitrary
44           version, the other project can be independently developed without
45           affecting the superproject, allowing the superproject project to
46           fix itself to new versions only when desired.
47
48        2. Splitting a (logically single) project into multiple repositories
49           and tying them back together. This can be used to overcome current
50           limitations of Git’s implementation to have finer grained access:
51
52           •   Size of the Git repository: In its current form Git scales up
53               poorly for large repositories containing content that is not
54               compressed by delta computation between trees. For example, you
55               can use submodules to hold large binary assets and these
56               repositories can be shallowly cloned such that you do not have
57               a large history locally.
58
59           •   Transfer size: In its current form Git requires the whole
60               working tree present. It does not allow partial trees to be
61               transferred in fetch or clone. If the project you work on
62               consists of multiple repositories tied together as submodules
63               in a superproject, you can avoid fetching the working trees of
64               the repositories you are not interested in.
65
66           •   Access control: By restricting user access to submodules, this
67               can be used to implement read/write policies for different
68               users.
69

THE CONFIGURATION OF SUBMODULES

71       Submodule operations can be configured using the following mechanisms
72       (from highest to lowest precedence):
73
74       •   The command line for those commands that support taking submodules
75           as part of their pathspecs. Most commands have a boolean flag
76           --recurse-submodules which specify whether to recurse into
77           submodules. Examples are grep and checkout. Some commands take
78           enums, such as fetch and push, where you can specify how submodules
79           are affected.
80
81       •   The configuration inside the submodule. This includes
82           $GIT_DIR/config in the submodule, but also settings in the tree
83           such as a .gitattributes or .gitignore files that specify behavior
84           of commands inside the submodule.
85
86           For example an effect from the submodule’s .gitignore file would be
87           observed when you run git status --ignore-submodules=none in the
88           superproject. This collects information from the submodule’s
89           working directory by running status in the submodule while paying
90           attention to the .gitignore file of the submodule.
91
92           The submodule’s $GIT_DIR/config file would come into play when
93           running git push --recurse-submodules=check in the superproject, as
94           this would check if the submodule has any changes not published to
95           any remote. The remotes are configured in the submodule as usual in
96           the $GIT_DIR/config file.
97
98       •   The configuration file $GIT_DIR/config in the superproject. Git
99           only recurses into active submodules (see "ACTIVE SUBMODULES"
100           section below).
101
102           If the submodule is not yet initialized, then the configuration
103           inside the submodule does not exist yet, so where to obtain the
104           submodule from is configured here for example.
105
106       •   The .gitmodules file inside the superproject. A project usually
107           uses this file to suggest defaults for the upstream collection of
108           repositories for the mapping that is required between a submodule’s
109           name and its path.
110
111           This file mainly serves as the mapping between the name and path of
112           submodules in the superproject, such that the submodule’s Git
113           directory can be located.
114
115           If the submodule has never been initialized, this is the only place
116           where submodule configuration is found. It serves as the last
117           fallback to specify where to obtain the submodule from.
118

FORMS

120       Submodules can take the following forms:
121
122       •   The basic form described in DESCRIPTION with a Git directory, a
123           working directory, a gitlink, and a .gitmodules entry.
124
125       •   "Old-form" submodule: A working directory with an embedded .git
126           directory, and the tracking gitlink and .gitmodules entry in the
127           superproject. This is typically found in repositories generated
128           using older versions of Git.
129
130           It is possible to construct these old form repositories manually.
131
132           When deinitialized or deleted (see below), the submodule’s Git
133           directory is automatically moved to $GIT_DIR/modules/<name>/ of the
134           superproject.
135
136       •   Deinitialized submodule: A gitlink, and a .gitmodules entry, but no
137           submodule working directory. The submodule’s Git directory may be
138           there as after deinitializing the Git directory is kept around. The
139           directory which is supposed to be the working directory is empty
140           instead.
141
142           A submodule can be deinitialized by running git submodule deinit.
143           Besides emptying the working directory, this command only modifies
144           the superproject’s $GIT_DIR/config file, so the superproject’s
145           history is not affected. This can be undone using git submodule
146           init.
147
148       •   Deleted submodule: A submodule can be deleted by running git rm
149           <submodule path> && git commit. This can be undone using git
150           revert.
151
152           The deletion removes the superproject’s tracking data, which are
153           both the gitlink entry and the section in the .gitmodules file. The
154           submodule’s working directory is removed from the file system, but
155           the Git directory is kept around as it to make it possible to
156           checkout past commits without requiring fetching from another
157           repository.
158
159           To completely remove a submodule, manually delete
160           $GIT_DIR/modules/<name>/.
161

ACTIVE SUBMODULES

163       A submodule is considered active,
164
165        1. if submodule.<name>.active is set to true
166
167           or
168
169        2. if the submodule’s path matches the pathspec in submodule.active
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171           or
172
173        3. if submodule.<name>.url is set.
174
175       and these are evaluated in this order.
176
177       For example:
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179           [submodule "foo"]
180             active = false
181             url = https://example.org/foo
182           [submodule "bar"]
183             active = true
184             url = https://example.org/bar
185           [submodule "baz"]
186             url = https://example.org/baz
187
188       In the above config only the submodule bar and baz are active, bar due
189       to (1) and baz due to (3). foo is inactive because (1) takes precedence
190       over (3)
191
192       Note that (3) is a historical artefact and will be ignored if the (1)
193       and (2) specify that the submodule is not active. In other words, if we
194       have a submodule.<name>.active set to false or if the submodule’s path
195       is excluded in the pathspec in submodule.active, the url doesn’t matter
196       whether it is present or not. This is illustrated in the example that
197       follows.
198
199           [submodule "foo"]
200             active = true
201             url = https://example.org/foo
202           [submodule "bar"]
203             url = https://example.org/bar
204           [submodule "baz"]
205             url = https://example.org/baz
206           [submodule "bob"]
207             ignore = true
208           [submodule]
209             active = b*
210             active = :(exclude) baz
211
212       In here all submodules except baz (foo, bar, bob) are active. foo due
213       to its own active flag and all the others due to the submodule active
214       pathspec, which specifies that any submodule starting with b except baz
215       are also active, regardless of the presence of the .url field.
216

WORKFLOW FOR A THIRD PARTY LIBRARY

218           # Add a submodule
219           git submodule add <url> <path>
220
221           # Occasionally update the submodule to a new version:
222           git -C <path> checkout <new version>
223           git add <path>
224           git commit -m "update submodule to new version"
225
226           # See the list of submodules in a superproject
227           git submodule status
228
229           # See FORMS on removing submodules
230

WORKFLOW FOR AN ARTIFICIALLY SPLIT REPO

232           # Enable recursion for relevant commands, such that
233           # regular commands recurse into submodules by default
234           git config --global submodule.recurse true
235
236           # Unlike most other commands below, clone still needs
237           # its own recurse flag:
238           git clone --recurse <URL> <directory>
239           cd <directory>
240
241           # Get to know the code:
242           git grep foo
243           git ls-files --recurse-submodules
244
245           Note
246           git ls-files also requires its own --recurse-submodules flag.
247
248           # Get new code
249           git fetch
250           git pull --rebase
251
252           # Change worktree
253           git checkout
254           git reset
255

IMPLEMENTATION DETAILS

257       When cloning or pulling a repository containing submodules the
258       submodules will not be checked out by default; you can instruct clone
259       to recurse into submodules. The init and update subcommands of git
260       submodule will maintain submodules checked out and at an appropriate
261       revision in your working tree. Alternatively you can set
262       submodule.recurse to have checkout recursing into submodules (note that
263       submodule.recurse also affects other Git commands, see git-config(1)
264       for a complete list).
265

SEE ALSO

267       git-submodule(1), gitmodules(5).
268

GIT

270       Part of the git(1) suite
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274Git 2.33.1                        2021-10-12                  GITSUBMODULES(7)
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