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Programming is an endless loop; it's either you break or exit.

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Date and Time

Environment Variables (draft)

Various Git commands use the following environment variables:

The Git Repository

These environment variables apply to all core Git commands. Nb: it is worth noting that they may be used/overridden by SCMS sitting above Git so take care if using a foreign front-end.

GIT_INDEX_FILE
This environment allows the specification of an alternate index file. If not specified, the default of $GIT_DIR/index is used.
GIT_INDEX_VERSION
This environment variable allows the specification of an index version for new repositories. It won’t affect existing index files. By default index file version 2 or 3 is used. See git-update-index(1) for more information.
GIT_OBJECT_DIRECTORY
If the object storage directory is specified via this environment variable then the sha1 directories are created underneath - otherwise the default $GIT_DIR/objects directory is used.
GIT_ALTERNATE_OBJECT_DIRECTORIES
Due to the immutable nature of Git objects, old objects can be archived into shared, read-only directories. This variable specifies a “:” separated (on Windows “;” separated) list of Git object directories which can be used to search for Git objects. New objects will not be written to these directories.
Entries that begin with `"` (double-quote) will be interpreted
as C-style quoted paths, removing leading and trailing
double-quotes and respecting backslash escapes. E.g., the value
`"path-with-\"-and-:-in-it":vanilla-path` has two paths:
`path-with-"-and-:-in-it` and `vanilla-path`.
GIT_DIR
If the GIT_DIR environment variable is set then it specifies a path to use instead of the default .git for the base of the repository. The --git-dir command-line option also sets this value.
GIT_WORK_TREE
Set the path to the root of the working tree. This can also be controlled by the --work-tree command-line option and the core.worktree configuration variable.
GIT_NAMESPACE
Set the Git namespace; see gitnamespaces(7) for details. The --namespace command-line option also sets this value.
GIT_CEILING_DIRECTORIES
This should be a colon-separated list of absolute paths. If set, it is a list of directories that Git should not chdir up into while looking for a repository directory (useful for excluding slow-loading network directories). It will not exclude the current working directory or a GIT_DIR set on the command line or in the environment. Normally, Git has to read the entries in this list and resolve any symlink that might be present in order to compare them with the current directory. However, if even this access is slow, you can add an empty entry to the list to tell Git that the subsequent entries are not symlinks and needn’t be resolved; e.g., GIT_CEILING_DIRECTORIES=/maybe/symlink::/very/slow/non/symlink.
GIT_DISCOVERY_ACROSS_FILESYSTEM
When run in a directory that does not have “.git” repository directory, Git tries to find such a directory in the parent directories to find the top of the working tree, but by default it does not cross filesystem boundaries. This environment variable can be set to true to tell Git not to stop at filesystem boundaries. Like GIT_CEILING_DIRECTORIES, this will not affect an explicit repository directory set via GIT_DIR or on the command line.
GIT_COMMON_DIR
If this variable is set to a path, non-worktree files that are normally in $GIT_DIR will be taken from this path instead. Worktree-specific files such as HEAD or index are taken from $GIT_DIR. See gitrepository-layout(5) and git-worktree(1) for details. This variable has lower precedence than other path variables such as GIT_INDEX_FILE, GIT_OBJECT_DIRECTORY…

Git Commits

GIT_AUTHOR_NAME
GIT_AUTHOR_EMAIL
GIT_AUTHOR_DATE
GIT_COMMITTER_NAME
GIT_COMMITTER_EMAIL
GIT_COMMITTER_DATE
EMAIL
see git-commit-tree(1)

Git Diffs

GIT_DIFF_OPTS
Only valid setting is "--unified=??" or "-u??" to set the number of context lines shown when a unified diff is created. This takes precedence over any "-U" or "--unified" option value passed on the Git diff command line.
GIT_EXTERNAL_DIFF
When the environment variable GIT_EXTERNAL_DIFF is set, the program named by it is called, instead of the diff invocation described above. For a path that is added, removed, or modified, GIT_EXTERNAL_DIFF is called with 7 parameters:
path old-file old-hex old-mode new-file new-hex new-mode
where:
<old|new>-file
are files GIT_EXTERNAL_DIFF can use to read the contents of <old|new>,
<old|new>-hex
are the 40-hexdigit SHA-1 hashes,
<old|new>-mode
are the octal representation of the file modes.
The file parameters can point at the user’s working file (e.g. new-file in “git-diff-files”), /dev/null (e.g. old-file when a new file is added), or a temporary file (e.g. old-file in the index). GIT_EXTERNAL_DIFF should not worry about unlinking the temporary file — it is removed when GIT_EXTERNAL_DIFF exits.
For a path that is unmerged, GIT_EXTERNAL_DIFF is called with 1 parameter, <path>;.
For each path GIT_EXTERNAL_DIFF is called, two environment variables, GIT_DIFF_PATH_COUNTER and GIT_DIFF_PATH_TOTAL are set.
GIT_DIFF_PATH_COUNTER
A 1-based counter incremented by one for every path.
GIT_DIFF_PATH_TOTAL
The total number of paths.

other

GIT_MERGE_VERBOSITY
A number controlling the amount of output shown by the recursive merge strategy. Overrides merge.verbosity. See git-merge(1)
GIT_PAGER
This environment variable overrides $PAGER. If it is set to an empty string or to the value “cat”, Git will not launch a pager. See also the core.pager option in git-config(1).
GIT_EDITOR
This environment variable overrides $EDITOR and $VISUAL. It is used by several Git commands when, on interactive mode, an editor is to be launched. See also git-var(1) and the core.editor option in git-config(1).
GIT_SSH
GIT_SSH_COMMAND
If either of these environment variables is set then git fetch and git push will use the specified command instead of ssh when they need to connect to a remote system. The command will be given exactly two or four arguments: the username@host (or just host) from the URL and the shell command to execute on that remote system, optionally preceded by -p (literally) and the port from the URL when it specifies something other than the default SSH port.
$GIT_SSH_COMMAND takes precedence over $GIT_SSH, and is interpreted by the shell, which allows additional arguments to be included. $GIT_SSH on the other hand must be just the path to a program (which can be a wrapper shell script, if additional arguments are needed).
Usually it is easier to configure any desired options through your personal .ssh/config file. Please consult your ssh documentation for further details.
GIT_SSH_VARIANT
If this environment variable is set, it overrides Git’s autodetection whether GIT_SSH/GIT_SSH_COMMAND/core.ssh Command refer to OpenSSH, plink or tortoiseplink. This variable overrides the config setting ssh.variant that serves the same purpose.
GIT_ASKPASS
If this environment variable is set, then Git commands which need to acquire passwords or passphrases (e.g. for HTTP or IMAP authentication) will call this program with a suitable prompt as command-line argument and read the password from its STDOUT. See also the core.askPass option in git-config(1).
GIT_TERMINAL_PROMPT
If this environment variable is set to 0, git will not prompt on the terminal (e.g., when asking for HTTP authentication).
GIT_CONFIG_NOSYSTEM
Whether to skip reading settings from the system-wide $(prefix)/etc/gitconfig file. This environment variable can be used along with $HOME and $XDG_CONFIG_HOME to create a predictable environment for a picky script, or you can set it temporarily to avoid using a buggy /etc/gitconfig file while waiting for someone with sufficient permissions to fix it.
GIT_FLUSH
If this environment variable is set to “1”, then commands such as git blame (in incremental mode), git rev-list, git log, git check-attr and git check-ignore will force a flush of the output stream after each record have been flushed. If this variable is set to “0”, the output of these commands will be done using completely buffered I/O. If this environment variable is not set, Git will choose buffered or record-oriented flushing based on whether stdout appears to be redirected to a file or not.
GIT_TRACE
Enables general trace messages, e.g. alias expansion, built-in command execution and external command execution.
If this variable is set to “1”, “2” or “true” (comparison is case insensitive), trace messages will be printed to stderr.
If the variable is set to an integer value greater than 2 and lower than 10 (strictly) then Git will interpret this value as an open file descriptor and will try to write the trace messages into this file descriptor.
Alternatively, if the variable is set to an absolute path (starting with a / character), Git will interpret this as a file path and will try to write the trace messages into it.
Unsetting the variable, or setting it to empty, “0” or “false” (case insensitive) disables trace messages.
GIT_TRACE_PACK_ACCESS
Enables trace messages for all accesses to any packs. For each access, the pack file name and an offset in the pack is recorded. This may be helpful for troubleshooting some pack-related performance problems. See GIT_TRACE for available trace output options.
GIT_TRACE_PACKET
Enables trace messages for all packets coming in or out of a given program. This can help with debugging object negotiation or other protocol issues. Tracing is turned off at a packet starting with “PACK” (but see GIT_TRACE_PACKFILE below). See GIT_TRACE for available trace output options.
GIT_TRACE_PACKFILE
Enables tracing of packfiles sent or received by a given program. Unlike other trace output, this trace is verbatim: no headers, and no quoting of binary data. You almost certainly want to direct into a file (e.g., GIT_TRACE_PACKFILE=/tmp/my.pack) rather than displaying it on the terminal or mixing it with other trace output.
Note that this is currently only implemented for the client side of clones and fetches.
GIT_TRACE_PERFORMANCE
Enables performance related trace messages, e.g. total execution time of each Git command. See GIT_TRACE for available trace output options.
GIT_TRACE_SETUP
Enables trace messages printing the .git, working tree and current working directory after Git has completed its setup phase. See GIT_TRACE for available trace output options.
GIT_TRACE_SHALLOW
Enables trace messages that can help debugging fetching / cloning of shallow repositories. See GIT_TRACE for available trace output options.
GIT_LITERAL_PATHSPECS
Setting this variable to 1 will cause Git to treat all pathspecs literally, rather than as glob patterns. For example, running GIT_LITERAL_PATHSPECS=1 git log -- '*.c' will search for commits that touch the path *.c, not any paths that the glob *.c matches. You might want this if you are feeding literal paths to Git (e.g., paths previously given to you by git ls-tree, --raw diff output, etc).
GIT_GLOB_PATHSPECS
Setting this variable to 1 will cause Git to treat all pathspecs as glob patterns (aka “glob” magic).
GIT_NOGLOB_PATHSPECS
Setting this variable to 1 will cause Git to treat all pathspecs as literal (aka “literal” magic).
GIT_ICASE_PATHSPECS
Setting this variable to 1 will cause Git to treat all pathspecs as case-insensitive.
GIT_REFLOG_ACTION
When a ref is updated, reflog entries are created to keep track of the reason why the ref was updated (which is typically the name of the high-level command that updated the ref), in addition to the old and new values of the ref. A scripted Porcelain command can use set_reflog_action helper function in git-sh-setup to set its name to this variable when it is invoked as the top level command by the end user, to be recorded in the body of the reflog.
GIT_REF_PARANOIA
If set to 1, include broken or badly named refs when iterating over lists of refs. In a normal, non-corrupted repository, this does nothing. However, enabling it may help git to detect and abort some operations in the presence of broken refs. Git sets this variable automatically when performing destructive operations like git-prune(1). You should not need to set it yourself unless you want to be paranoid about making sure an operation has touched every ref (e.g., because you are cloning a repository to make a backup).
GIT_ALLOW_PROTOCOL
If set, provide a colon-separated list of protocols which are allowed to be used with fetch/push/clone. This is useful to restrict recursive submodule initialization from an untrusted repository. Any protocol not mentioned will be disallowed (i.e., this is a whitelist, not a blacklist). If the variable is not set at all, all protocols are enabled. The protocol names currently used by git are:
  • file: any local file-based path (including file:// URLs, or local paths)

  • git: the anonymous git protocol over a direct TCP connection (or proxy, if configured)

  • ssh: git over ssh (including host:path syntax, ssh://, etc).

  • http: git over http, both “smart http” and “dumb http”. Note that this does not include https; if you want both, you should specify both as http:https.

  • any external helpers are named by their protocol (e.g., use hg to allow the git-remote-hg helper)