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diff --git a/Documentation/gitfaq.txt b/Documentation/gitfaq.txt new file mode 100644 index 0000000000..afdaeab850 --- /dev/null +++ b/Documentation/gitfaq.txt @@ -0,0 +1,441 @@ +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 +------------- + +[[user-name]] +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 linkgit:git-config[1]. + +[[http-postbuffer]] +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. + +[[configure-editor]] +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 linkgit: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 +----------- + +[[http-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. + +[[http-credentials-environment]] +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=$GIT_TOKEN"; };f' +---- + +[[http-reset-credentials]] +How do I change the password or token I've saved in my credential manager?:: + Usually, if the password or token is invalid, Git will erase it and + prompt for a new one. However, there are times when this doesn't always + happen. To change the password or token, you can erase the existing + credentials and then Git will prompt for new ones. To erase + credentials, use a syntax like the following (substituting your username + and the hostname): ++ +---- +$ echo url=https://author@git.example.org | git credential reject +---- + +[[multiple-accounts-http]] +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 + linkgit:git-remote[1] for details). + +[[multiple-accounts-ssh]] +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 +------------- + +[[last-commit-amend]] +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. + +[[undo-previous-change]] +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. + +[[ignore-tracked-files]] +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. + +[[files-in-gitignore-are-tracked]] +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 linkgit:gitignore[5] for details. + +[[fetching-and-pulling]] +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 linkgit:git-pull[1]. + +Merging and Rebasing +-------------------- + +[[long-running-squash-merge]] +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. + +[[merge-two-revert-one]] +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 recursive + 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 linkgit:git-rebase[1] for more details. + +Hooks +----- + +[[restrict-with-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 +--------------------- + +[[windows-text-binary]] +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 + linkgit:git-diff[1] to work as expected, while still allowing your tools + to work. ++ +To do so, you can specify a linkgit: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 `$GIT_DIR/info/attributes`, since making it in a `.gitattributes` file in the +repository will apply to all users of the repository. ++ +See the following entry for information about normalizing line endings as well, +and see linkgit:gitattributes[5] for more information about attribute files. + +[[windows-diff-control-m]] +I'm on Windows and git diff shows my files as having a `^M` at the end.:: + By default, Git expects files to be stored with Unix line endings. As such, + the carriage return (`^M`) that is part of a Windows line ending is shown + because it is considered to be trailing whitespace. Git defaults to showing + trailing whitespace only on new lines, not existing ones. ++ +You can store the files in the repository with Unix line endings and convert +them automatically to your platform's line endings. To do that, set the +configuration option `core.eol` to `native` and see the following entry for +information about how to configure files as text or binary. ++ +You can also control this behavior with the `core.whitespace` setting if you +don't wish to remove the carriage returns from your line endings. + +[[always-modified-files-case]] +Why do I have a file that's always modified?:: + Internally, Git always stores file names as sequences of bytes and doesn't + perform any encoding or case folding. However, Windows and macOS by default + both perform case folding on file names. As a result, it's possible to end up + with multiple files or directories whose names differ only in case. Git can + handle this just fine, but the file system can store only one of these files, + so when Git reads the other file to see its contents, it looks modified. ++ +It's best to remove one of the files such that you only have one file. You can +do this with commands like the following (assuming two files `AFile.txt` and +`afile.txt`) on an otherwise clean working tree: ++ +---- +$ 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 . +---- + +[[recommended-storage-settings]] +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 linkgit: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 linkgit:git[1] suite |