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GITFAQ(7) Git Manual GITFAQ(7)
NAME
gitfaq - Frequently asked questions about using Git
SYNOPSIS
gitfaq
DESCRIPTION
The examples in this FAQ assume a standard POSIX shell, like bash or
dash, and a user, A U Thor, who has the account author on the hosting
provider git.example.org.
CONFIGURATION
What should I put in user.name?
You should put your personal name, generally a form using a given
name and family name. For example, the current maintainer of Git
uses "Junio C Hamano". This will be the name portion that is stored
in every commit you make.
This configuration doesn't have any effect on authenticating to
remote services; for that, see credential.username in git-
config(1).
What does http.postBuffer really do?
This option changes the size of the buffer that Git uses when
pushing data to a remote over HTTP or HTTPS. If the data is larger
than this size, libcurl, which handles the HTTP support for Git,
will use chunked transfer encoding since it isn't known ahead of
time what the size of the pushed data will be.
Leaving this value at the default size is fine unless you know that
either the remote server or a proxy in the middle doesn't support
HTTP/1.1 (which introduced the chunked transfer encoding) or is
known to be broken with chunked data. This is often (erroneously)
suggested as a solution for generic push problems, but since almost
every server and proxy supports at least HTTP/1.1, raising this
value usually doesn't solve most push problems. A server or proxy
that didn't correctly support HTTP/1.1 and chunked transfer
encoding wouldn't be that useful on the Internet today, since it
would break lots of traffic.
Note that increasing this value will increase the memory used on
every relevant push that Git does over HTTP or HTTPS, since the
entire buffer is allocated regardless of whether or not it is all
used. Thus, it's best to leave it at the default unless you are
sure you need a different value.
How do I configure a different editor?
If you haven't specified an editor specifically for Git, it will by
default use the editor you've configured using the VISUAL or EDITOR
environment variables, or if neither is specified, the system
default (which is usually vi). Since some people find vi difficult
to use or prefer a different editor, it may be desirable to change
the editor used.
If you want to configure a general editor for most programs which
need one, you can edit your shell configuration (e.g., ~/.bashrc or
~/.zshenv) to contain a line setting the EDITOR or VISUAL
environment variable to an appropriate value. For example, if you
prefer the editor nano, then you could write the following:
export VISUAL=nano
If you want to configure an editor specifically for Git, you can
either set the core.editor configuration value or the GIT_EDITOR
environment variable. You can see git-var(1) for details on the
order in which these options are consulted.
Note that in all cases, the editor value will be passed to the
shell, so any arguments containing spaces should be appropriately
quoted. Additionally, if your editor normally detaches from the
terminal when invoked, you should specify it with an argument that
makes it not do that, or else Git will not see any changes. An
example of a configuration addressing both of these issues on
Windows would be the configuration "C:\Program Files\Vim\gvim.exe"
--nofork, which quotes the filename with spaces and specifies the
--nofork option to avoid backgrounding the process.
CREDENTIALS
How do I specify my credentials when pushing over HTTP?
The easiest way to do this is to use a credential helper via the
credential.helper configuration. Most systems provide a standard
choice to integrate with the system credential manager. For
example, Git for Windows provides the wincred credential manager,
macOS has the osxkeychain credential manager, and Unix systems with
a standard desktop environment can use the libsecret credential
manager. All of these store credentials in an encrypted store to
keep your passwords or tokens secure.
In addition, you can use the store credential manager which stores
in a file in your home directory, or the cache credential manager,
which does not permanently store your credentials, but does prevent
you from being prompted for them for a certain period of time.
You can also just enter your password when prompted. While it is
possible to place the password (which must be percent-encoded) in
the URL, this is not particularly secure and can lead to accidental
exposure of credentials, so it is not recommended.
How do I read a password or token from an environment variable?
The credential.helper configuration option can also take an
arbitrary shell command that produces the credential protocol on
standard output. This is useful when passing credentials into a
container, for example.
Such a shell command can be specified by starting the option value
with an exclamation point. If your password or token were stored in
the GIT_TOKEN, you could run the following command to set your
credential helper:
$ git config credential.helper \
'!f() { echo username=author; echo "password=$GIT_TOKEN"; };f'
How do I change the password or token I've saved in my credential
manager?
Usually, if the password or token is invalid, Git will erase it and
prompt for a new one. However, there are times when this doesn't
always happen. To change the password or token, you can erase the
existing credentials and then Git will prompt for new ones. To
erase credentials, use a syntax like the following (substituting
your username and the hostname):
$ echo url=https://author@git.example.org | git credential reject
How do I use multiple accounts with the same hosting provider using
HTTP?
Usually the easiest way to distinguish between these accounts is to
use the username in the URL. For example, if you have the accounts
author and committer on git.example.org, you can use the URLs
https://author@git.example.org/org1/project1.git and
https://committer@git.example.org/org2/project2.git. This way, when
you use a credential helper, it will automatically try to look up
the correct credentials for your account. If you already have a
remote set up, you can change the URL with something like git
remote set-url origin
https://author@git.example.org/org1/project1.git (see git-remote(1)
for details).
How do I use multiple accounts with the same hosting provider using
SSH?
With most hosting providers that support SSH, a single key pair
uniquely identifies a user. Therefore, to use multiple accounts,
it's necessary to create a key pair for each account. If you're
using a reasonably modern OpenSSH version, you can create a new key
pair with something like ssh-keygen -t ed25519 -f
~/.ssh/id_committer. You can then register the public key (in this
case, ~/.ssh/id_committer.pub; note the .pub) with the hosting
provider.
Most hosting providers use a single SSH account for pushing; that
is, all users push to the git account (e.g., git@git.example.org).
If that's the case for your provider, you can set up multiple
aliases in SSH to make it clear which key pair to use. For example,
you could write something like the following in ~/.ssh/config,
substituting the proper private key file:
# This is the account for author on git.example.org.
Host example_author
HostName git.example.org
User git
# This is the key pair registered for author with git.example.org.
IdentityFile ~/.ssh/id_author
IdentitiesOnly yes
# This is the account for committer on git.example.org.
Host example_committer
HostName git.example.org
User git
# This is the key pair registered for committer with git.example.org.
IdentityFile ~/.ssh/id_committer
IdentitiesOnly yes
Then, you can adjust your push URL to use git@example_author or
git@example_committer instead of git@example.org (e.g., git remote
set-url git@example_author:org1/project1.git).
COMMON ISSUES
I've made a mistake in the last commit. How do I change it?
You can make the appropriate change to your working tree, run git
add <file> or git rm <file>, as appropriate, to stage it, and then
git commit --amend. Your change will be included in the commit, and
you'll be prompted to edit the commit message again; if you wish to
use the original message verbatim, you can use the --no-edit option
to git commit in addition, or just save and quit when your editor
opens.
I've made a change with a bug and it's been included in the main
branch. How should I undo it?
The usual way to deal with this is to use git revert. This
preserves the history that the original change was made and was a
valuable contribution, but also introduces a new commit that undoes
those changes because the original had a problem. The commit
message of the revert indicates the commit which was reverted and
is usually edited to include an explanation as to why the revert
was made.
How do I ignore changes to a tracked file?
Git doesn't provide a way to do this. The reason is that if Git
needs to overwrite this file, such as during a checkout, it doesn't
know whether the changes to the file are precious and should be
kept, or whether they are irrelevant and can safely be destroyed.
Therefore, it has to take the safe route and always preserve them.
It's tempting to try to use certain features of git update-index,
namely the assume-unchanged and skip-worktree bits, but these don't
work properly for this purpose and shouldn't be used this way.
If your goal is to modify a configuration file, it can often be
helpful to have a file checked into the repository which is a
template or set of defaults which can then be copied alongside and
modified as appropriate. This second, modified file is usually
ignored to prevent accidentally committing it.
I asked Git to ignore various files, yet they are still tracked
A gitignore file ensures that certain file(s) which are not tracked
by Git remain untracked. However, sometimes particular file(s) may
have been tracked before adding them into the .gitignore, hence
they still remain tracked. To untrack and ignore files/patterns,
use git rm --cached <file/pattern> and add a pattern to .gitignore
that matches the <file>. See gitignore(5) for details.
How do I know if I want to do a fetch or a pull?
A fetch stores a copy of the latest changes from the remote
repository, without modifying the working tree or current branch.
You can then at your leisure inspect, merge, rebase on top of, or
ignore the upstream changes. A pull consists of a fetch followed
immediately by either a merge or rebase. See git-pull(1).
MERGING AND REBASING
What kinds of problems can occur when merging long-lived branches with
squash merges?
In general, there are a variety of problems that can occur when
using squash merges to merge two branches multiple times. These can
include seeing extra commits in git log output, with a GUI, or when
using the ... notation to express a range, as well as the
possibility of needing to re-resolve conflicts again and again.
When Git does a normal merge between two branches, it considers
exactly three points: the two branches and a third commit, called
the merge base, which is usually the common ancestor of the
commits. The result of the merge is the sum of the changes between
the merge base and each head. When you merge two branches with a
regular merge commit, this results in a new commit which will end
up as a merge base when they're merged again, because there is now
a new common ancestor. Git doesn't have to consider changes that
occurred before the merge base, so you don't have to re-resolve any
conflicts you resolved before.
When you perform a squash merge, a merge commit isn't created;
instead, the changes from one side are applied as a regular commit
to the other side. This means that the merge base for these
branches won't have changed, and so when Git goes to perform its
next merge, it considers all of the changes that it considered the
last time plus the new changes. That means any conflicts may need
to be re-resolved. Similarly, anything using the ... notation in
git diff, git log, or a GUI will result in showing all of the
changes since the original merge base.
As a consequence, if you want to merge two long-lived branches
repeatedly, it's best to always use a regular merge commit.
If I make a change on two branches but revert it on one, why does the
merge of those branches include the change?
By default, when Git does a merge, it uses a strategy called the
ort strategy, which does a fancy three-way merge. In such a case,
when Git performs the merge, it considers exactly three points: the
two heads and a third point, called the merge base, which is
usually the common ancestor of those commits. Git does not consider
the history or the individual commits that have happened on those
branches at all.
As a result, if both sides have a change and one side has reverted
that change, the result is to include the change. This is because
the code has changed on one side and there is no net change on the
other, and in this scenario, Git adopts the change.
If this is a problem for you, you can do a rebase instead, rebasing
the branch with the revert onto the other branch. A rebase in this
scenario will revert the change, because a rebase applies each
individual commit, including the revert. Note that rebases rewrite
history, so you should avoid rebasing published branches unless
you're sure you're comfortable with that. See the NOTES section in
git-rebase(1) for more details.
HOOKS
How do I use hooks to prevent users from making certain changes?
The only safe place to make these changes is on the remote
repository (i.e., the Git server), usually in the pre-receive hook
or in a continuous integration (CI) system. These are the locations
in which policy can be enforced effectively.
It's common to try to use pre-commit hooks (or, for commit
messages, commit-msg hooks) to check these things, which is great
if you're working as a solo developer and want the tooling to help
you. However, using hooks on a developer machine is not effective
as a policy control because a user can bypass these hooks with
--no-verify without being noticed (among various other ways). Git
assumes that the user is in control of their local repositories and
doesn't try to prevent this or tattle on the user.
In addition, some advanced users find pre-commit hooks to be an
impediment to workflows that use temporary commits to stage work in
progress or that create fixup commits, so it's better to push these
kinds of checks to the server anyway.
CROSS-PLATFORM ISSUES
I'm on Windows and my text files are detected as binary.
Git works best when you store text files as UTF-8. Many programs on
Windows support UTF-8, but some do not and only use the
little-endian UTF-16 format, which Git detects as binary. If you
can't use UTF-8 with your programs, you can specify a working tree
encoding that indicates which encoding your files should be checked
out with, while still storing these files as UTF-8 in the
repository. This allows tools like git-diff(1) to work as expected,
while still allowing your tools to work.
To do so, you can specify a gitattributes(5) pattern with the
working-tree-encoding attribute. For example, the following pattern
sets all C files to use UTF-16LE-BOM, which is a common encoding on
Windows:
*.c working-tree-encoding=UTF-16LE-BOM
You will need to run git add --renormalize to have this take
effect. Note that if you are making these changes on a project that
is used across platforms, you'll probably want to make it in a
per-user configuration file or in the one in
$GIT_DIR/info/attributes, since making it in a .gitattributes file
in the repository will apply to all users of the repository.
See the following entry for information about normalizing line
endings as well, and see gitattributes(5) for more information
about attribute files.
I'm on Windows and git diff shows my files as having a ^M at the end.
By default, Git expects files to be stored with Unix line endings.
As such, the carriage return (^M) that is part of a Windows line
ending is shown because it is considered to be trailing whitespace.
Git defaults to showing trailing whitespace only on new lines, not
existing ones.
You can store the files in the repository with Unix line endings
and convert them automatically to your platform's line endings. To
do that, set the configuration option core.eol to native and see
the following entry for information about how to configure files as
text or binary.
You can also control this behavior with the core.whitespace setting
if you don't wish to remove the carriage returns from your line
endings.
Why do I have a file that's always modified?
Internally, Git always stores file names as sequences of bytes and
doesn't perform any encoding or case folding. However, Windows and
macOS by default both perform case folding on file names. As a
result, it's possible to end up with multiple files or directories
whose names differ only in case. Git can handle this just fine, but
the file system can store only one of these files, so when Git
reads the other file to see its contents, it looks modified.
It's best to remove one of the files such that you only have one
file. You can do this with commands like the following (assuming
two files AFile.txt and afile.txt) on an otherwise clean working
tree:
$ git rm --cached AFile.txt
$ git commit -m 'Remove files conflicting in case'
$ git checkout .
This avoids touching the disk, but removes the additional file.
Your project may prefer to adopt a naming convention, such as
all-lowercase names, to avoid this problem from occurring again;
such a convention can be checked using a pre-receive hook or as
part of a continuous integration (CI) system.
It is also possible for perpetually modified files to occur on any
platform if a smudge or clean filter is in use on your system but a
file was previously committed without running the smudge or clean
filter. To fix this, run the following on an otherwise clean
working tree:
$ git add --renormalize .
What's the recommended way to store files in Git?
While Git can store and handle any file of any type, there are some
settings that work better than others. In general, we recommend
that text files be stored in UTF-8 without a byte-order mark (BOM)
with LF (Unix-style) endings. We also recommend the use of UTF-8
(again, without BOM) in commit messages. These are the settings
that work best across platforms and with tools such as git diff and
git merge.
Additionally, if you have a choice between storage formats that are
text based or non-text based, we recommend storing files in the
text format and, if necessary, transforming them into the other
format. For example, a text-based SQL dump with one record per line
will work much better for diffing and merging than an actual
database file. Similarly, text-based formats such as Markdown and
AsciiDoc will work better than binary formats such as Microsoft
Word and PDF.
Similarly, storing binary dependencies (e.g., shared libraries or
JAR files) or build products in the repository is generally not
recommended. Dependencies and build products are best stored on an
artifact or package server with only references, URLs, and hashes
stored in the repository.
We also recommend setting a gitattributes(5) file to explicitly
mark which files are text and which are binary. If you want Git to
guess, you can set the attribute text=auto. For example, the
following might be appropriate in some projects:
# By default, guess.
* text=auto
# Mark all C files as text.
*.c text
# Mark all JPEG files as binary.
*.jpg binary
These settings help tools pick the right format for output such as
patches and result in files being checked out in the appropriate
line ending for the platform.
GIT
Part of the git(1) suite
Git 2.41.0 2023-06-01 GITFAQ(7)