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+git-update-index(1)
+===================
+
+NAME
+----
+git-update-index - Register file contents in the working tree to the index
+
+
+SYNOPSIS
+--------
+[verse]
+'git update-index'
+	     [--add] [--remove | --force-remove] [--replace]
+	     [--refresh] [-q] [--unmerged] [--ignore-missing]
+	     [(--cacheinfo <mode>,<object>,<file>)...]
+	     [--chmod=(+|-)x]
+	     [--[no-]assume-unchanged]
+	     [--[no-]skip-worktree]
+	     [--[no-]fsmonitor-valid]
+	     [--ignore-submodules]
+	     [--[no-]split-index]
+	     [--[no-|test-|force-]untracked-cache]
+	     [--[no-]fsmonitor]
+	     [--really-refresh] [--unresolve] [--again | -g]
+	     [--info-only] [--index-info]
+	     [-z] [--stdin] [--index-version <n>]
+	     [--verbose]
+	     [--] [<file>...]
+
+DESCRIPTION
+-----------
+Modifies the index or directory cache. Each file mentioned is updated
+into the index and any 'unmerged' or 'needs updating' state is
+cleared.
+
+See also linkgit:git-add[1] for a more user-friendly way to do some of
+the most common operations on the index.
+
+The way 'git update-index' handles files it is told about can be modified
+using the various options:
+
+OPTIONS
+-------
+--add::
+	If a specified file isn't in the index already then it's
+	added.
+	Default behaviour is to ignore new files.
+
+--remove::
+	If a specified file is in the index but is missing then it's
+	removed.
+	Default behavior is to ignore removed file.
+
+--refresh::
+	Looks at the current index and checks to see if merges or
+	updates are needed by checking stat() information.
+
+-q::
+        Quiet.  If --refresh finds that the index needs an update, the
+        default behavior is to error out.  This option makes
+	'git update-index' continue anyway.
+
+--ignore-submodules::
+	Do not try to update submodules.  This option is only respected
+	when passed before --refresh.
+
+--unmerged::
+        If --refresh finds unmerged changes in the index, the default
+	behavior is to error out.  This option makes 'git update-index'
+        continue anyway.
+
+--ignore-missing::
+	Ignores missing files during a --refresh
+
+--cacheinfo <mode>,<object>,<path>::
+--cacheinfo <mode> <object> <path>::
+	Directly insert the specified info into the index.  For
+	backward compatibility, you can also give these three
+	arguments as three separate parameters, but new users are
+	encouraged to use a single-parameter form.
+
+--index-info::
+        Read index information from stdin.
+
+--chmod=(+|-)x::
+        Set the execute permissions on the updated files.
+
+--[no-]assume-unchanged::
+	When this flag is specified, the object names recorded
+	for the paths are not updated.  Instead, this option
+	sets/unsets the "assume unchanged" bit for the
+	paths.  When the "assume unchanged" bit is on, the user
+	promises not to change the file and allows Git to assume
+	that the working tree file matches what is recorded in
+	the index.  If you want to change the working tree file,
+	you need to unset the bit to tell Git.  This is
+	sometimes helpful when working with a big project on a
+	filesystem that has very slow lstat(2) system call
+	(e.g. cifs).
++
+Git will fail (gracefully) in case it needs to modify this file
+in the index e.g. when merging in a commit;
+thus, in case the assumed-untracked file is changed upstream,
+you will need to handle the situation manually.
+
+--really-refresh::
+	Like `--refresh`, but checks stat information unconditionally,
+	without regard to the "assume unchanged" setting.
+
+--[no-]skip-worktree::
+	When one of these flags is specified, the object name recorded
+	for the paths are not updated. Instead, these options
+	set and unset the "skip-worktree" bit for the paths. See
+	section "Skip-worktree bit" below for more information.
+
+--[no-]fsmonitor-valid::
+	When one of these flags is specified, the object name recorded
+	for the paths are not updated. Instead, these options
+	set and unset the "fsmonitor valid" bit for the paths. See
+	section "File System Monitor" below for more information.
+
+-g::
+--again::
+	Runs 'git update-index' itself on the paths whose index
+	entries are different from those from the `HEAD` commit.
+
+--unresolve::
+	Restores the 'unmerged' or 'needs updating' state of a
+	file during a merge if it was cleared by accident.
+
+--info-only::
+	Do not create objects in the object database for all
+	<file> arguments that follow this flag; just insert
+	their object IDs into the index.
+
+--force-remove::
+	Remove the file from the index even when the working directory
+	still has such a file. (Implies --remove.)
+
+--replace::
+	By default, when a file `path` exists in the index,
+	'git update-index' refuses an attempt to add `path/file`.
+	Similarly if a file `path/file` exists, a file `path`
+	cannot be added.  With --replace flag, existing entries
+	that conflict with the entry being added are
+	automatically removed with warning messages.
+
+--stdin::
+	Instead of taking list of paths from the command line,
+	read list of paths from the standard input.  Paths are
+	separated by LF (i.e. one path per line) by default.
+
+--verbose::
+        Report what is being added and removed from index.
+
+--index-version <n>::
+	Write the resulting index out in the named on-disk format version.
+	Supported versions are 2, 3 and 4. The current default version is 2
+	or 3, depending on whether extra features are used, such as
+	`git add -N`.
++
+Version 4 performs a simple pathname compression that reduces index
+size by 30%-50% on large repositories, which results in faster load
+time. Version 4 is relatively young (first released in 1.8.0 in
+October 2012). Other Git implementations such as JGit and libgit2
+may not support it yet.
+
+-z::
+	Only meaningful with `--stdin` or `--index-info`; paths are
+	separated with NUL character instead of LF.
+
+--split-index::
+--no-split-index::
+	Enable or disable split index mode. If split-index mode is
+	already enabled and `--split-index` is given again, all
+	changes in $GIT_DIR/index are pushed back to the shared index
+	file.
++
+These options take effect whatever the value of the `core.splitIndex`
+configuration variable (see linkgit:git-config[1]). But a warning is
+emitted when the change goes against the configured value, as the
+configured value will take effect next time the index is read and this
+will remove the intended effect of the option.
+
+--untracked-cache::
+--no-untracked-cache::
+	Enable or disable untracked cache feature. Please use
+	`--test-untracked-cache` before enabling it.
++
+These options take effect whatever the value of the `core.untrackedCache`
+configuration variable (see linkgit:git-config[1]). But a warning is
+emitted when the change goes against the configured value, as the
+configured value will take effect next time the index is read and this
+will remove the intended effect of the option.
+
+--test-untracked-cache::
+	Only perform tests on the working directory to make sure
+	untracked cache can be used. You have to manually enable
+	untracked cache using `--untracked-cache` or
+	`--force-untracked-cache` or the `core.untrackedCache`
+	configuration variable afterwards if you really want to use
+	it. If a test fails the exit code is 1 and a message
+	explains what is not working as needed, otherwise the exit
+	code is 0 and OK is printed.
+
+--force-untracked-cache::
+	Same as `--untracked-cache`. Provided for backwards
+	compatibility with older versions of Git where
+	`--untracked-cache` used to imply `--test-untracked-cache` but
+	this option would enable the extension unconditionally.
+
+--fsmonitor::
+--no-fsmonitor::
+	Enable or disable files system monitor feature. These options
+	take effect whatever the value of the `core.fsmonitor`
+	configuration variable (see linkgit:git-config[1]). But a warning
+	is emitted when the change goes against the configured value, as
+	the configured value will take effect next time the index is
+	read and this will remove the intended effect of the option.
+
+\--::
+	Do not interpret any more arguments as options.
+
+<file>::
+	Files to act on.
+	Note that files beginning with '.' are discarded. This includes
+	`./file` and `dir/./file`. If you don't want this, then use
+	cleaner names.
+	The same applies to directories ending '/' and paths with '//'
+
+USING --REFRESH
+---------------
+`--refresh` does not calculate a new sha1 file or bring the index
+up to date for mode/content changes. But what it *does* do is to
+"re-match" the stat information of a file with the index, so that you
+can refresh the index for a file that hasn't been changed but where
+the stat entry is out of date.
+
+For example, you'd want to do this after doing a 'git read-tree', to link
+up the stat index details with the proper files.
+
+USING --CACHEINFO OR --INFO-ONLY
+--------------------------------
+`--cacheinfo` is used to register a file that is not in the
+current working directory.  This is useful for minimum-checkout
+merging.
+
+To pretend you have a file at path with mode and sha1, say:
+
+----------------
+$ git update-index --add --cacheinfo <mode>,<sha1>,<path>
+----------------
+
+`--info-only` is used to register files without placing them in the object
+database.  This is useful for status-only repositories.
+
+Both `--cacheinfo` and `--info-only` behave similarly: the index is updated
+but the object database isn't.  `--cacheinfo` is useful when the object is
+in the database but the file isn't available locally.  `--info-only` is
+useful when the file is available, but you do not wish to update the
+object database.
+
+
+USING --INDEX-INFO
+------------------
+
+`--index-info` is a more powerful mechanism that lets you feed
+multiple entry definitions from the standard input, and designed
+specifically for scripts.  It can take inputs of three formats:
+
+    . mode SP type SP sha1          TAB path
++
+This format is to stuff `git ls-tree` output into the index.
+
+    . mode         SP sha1 SP stage TAB path
++
+This format is to put higher order stages into the
+index file and matches 'git ls-files --stage' output.
+
+    . mode         SP sha1          TAB path
++
+This format is no longer produced by any Git command, but is
+and will continue to be supported by `update-index --index-info`.
+
+To place a higher stage entry to the index, the path should
+first be removed by feeding a mode=0 entry for the path, and
+then feeding necessary input lines in the third format.
+
+For example, starting with this index:
+
+------------
+$ git ls-files -s
+100644 8a1218a1024a212bb3db30becd860315f9f3ac52 0       frotz
+------------
+
+you can feed the following input to `--index-info`:
+
+------------
+$ git update-index --index-info
+0 0000000000000000000000000000000000000000	frotz
+100644 8a1218a1024a212bb3db30becd860315f9f3ac52 1	frotz
+100755 8a1218a1024a212bb3db30becd860315f9f3ac52 2	frotz
+------------
+
+The first line of the input feeds 0 as the mode to remove the
+path; the SHA-1 does not matter as long as it is well formatted.
+Then the second and third line feeds stage 1 and stage 2 entries
+for that path.  After the above, we would end up with this:
+
+------------
+$ git ls-files -s
+100644 8a1218a1024a212bb3db30becd860315f9f3ac52 1	frotz
+100755 8a1218a1024a212bb3db30becd860315f9f3ac52 2	frotz
+------------
+
+
+USING ``ASSUME UNCHANGED'' BIT
+------------------------------
+
+Many operations in Git depend on your filesystem to have an
+efficient `lstat(2)` implementation, so that `st_mtime`
+information for working tree files can be cheaply checked to see
+if the file contents have changed from the version recorded in
+the index file.  Unfortunately, some filesystems have
+inefficient `lstat(2)`.  If your filesystem is one of them, you
+can set "assume unchanged" bit to paths you have not changed to
+cause Git not to do this check.  Note that setting this bit on a
+path does not mean Git will check the contents of the file to
+see if it has changed -- it makes Git to omit any checking and
+assume it has *not* changed.  When you make changes to working
+tree files, you have to explicitly tell Git about it by dropping
+"assume unchanged" bit, either before or after you modify them.
+
+In order to set "assume unchanged" bit, use `--assume-unchanged`
+option.  To unset, use `--no-assume-unchanged`. To see which files
+have the "assume unchanged" bit set, use `git ls-files -v`
+(see linkgit:git-ls-files[1]).
+
+The command looks at `core.ignorestat` configuration variable.  When
+this is true, paths updated with `git update-index paths...` and
+paths updated with other Git commands that update both index and
+working tree (e.g. 'git apply --index', 'git checkout-index -u',
+and 'git read-tree -u') are automatically marked as "assume
+unchanged".  Note that "assume unchanged" bit is *not* set if
+`git update-index --refresh` finds the working tree file matches
+the index (use `git update-index --really-refresh` if you want
+to mark them as "assume unchanged").
+
+
+EXAMPLES
+--------
+To update and refresh only the files already checked out:
+
+----------------
+$ git checkout-index -n -f -a && git update-index --ignore-missing --refresh
+----------------
+
+On an inefficient filesystem with `core.ignorestat` set::
++
+------------
+$ git update-index --really-refresh              <1>
+$ git update-index --no-assume-unchanged foo.c   <2>
+$ git diff --name-only                           <3>
+$ edit foo.c
+$ git diff --name-only                           <4>
+M foo.c
+$ git update-index foo.c                         <5>
+$ git diff --name-only                           <6>
+$ edit foo.c
+$ git diff --name-only                           <7>
+$ git update-index --no-assume-unchanged foo.c   <8>
+$ git diff --name-only                           <9>
+M foo.c
+------------
++
+<1> forces lstat(2) to set "assume unchanged" bits for paths that match index.
+<2> mark the path to be edited.
+<3> this does lstat(2) and finds index matches the path.
+<4> this does lstat(2) and finds index does *not* match the path.
+<5> registering the new version to index sets "assume unchanged" bit.
+<6> and it is assumed unchanged.
+<7> even after you edit it.
+<8> you can tell about the change after the fact.
+<9> now it checks with lstat(2) and finds it has been changed.
+
+
+SKIP-WORKTREE BIT
+-----------------
+
+Skip-worktree bit can be defined in one (long) sentence: When reading
+an entry, if it is marked as skip-worktree, then Git pretends its
+working directory version is up to date and read the index version
+instead.
+
+To elaborate, "reading" means checking for file existence, reading
+file attributes or file content. The working directory version may be
+present or absent. If present, its content may match against the index
+version or not. Writing is not affected by this bit, content safety
+is still first priority. Note that Git _can_ update working directory
+file, that is marked skip-worktree, if it is safe to do so (i.e.
+working directory version matches index version)
+
+Although this bit looks similar to assume-unchanged bit, its goal is
+different from assume-unchanged bit's. Skip-worktree also takes
+precedence over assume-unchanged bit when both are set.
+
+SPLIT INDEX
+-----------
+
+This mode is designed for repositories with very large indexes, and
+aims at reducing the time it takes to repeatedly write these indexes.
+
+In this mode, the index is split into two files, $GIT_DIR/index and
+$GIT_DIR/sharedindex.<SHA-1>. Changes are accumulated in
+$GIT_DIR/index, the split index, while the shared index file contains
+all index entries and stays unchanged.
+
+All changes in the split index are pushed back to the shared index
+file when the number of entries in the split index reaches a level
+specified by the splitIndex.maxPercentChange config variable (see
+linkgit:git-config[1]).
+
+Each time a new shared index file is created, the old shared index
+files are deleted if their modification time is older than what is
+specified by the splitIndex.sharedIndexExpire config variable (see
+linkgit:git-config[1]).
+
+To avoid deleting a shared index file that is still used, its
+modification time is updated to the current time everytime a new split
+index based on the shared index file is either created or read from.
+
+UNTRACKED CACHE
+---------------
+
+This cache is meant to speed up commands that involve determining
+untracked files such as `git status`.
+
+This feature works by recording the mtime of the working tree
+directories and then omitting reading directories and stat calls
+against files in those directories whose mtime hasn't changed. For
+this to work the underlying operating system and file system must
+change the `st_mtime` field of directories if files in the directory
+are added, modified or deleted.
+
+You can test whether the filesystem supports that with the
+`--test-untracked-cache` option. The `--untracked-cache` option used
+to implicitly perform that test in older versions of Git, but that's
+no longer the case.
+
+If you want to enable (or disable) this feature, it is easier to use
+the `core.untrackedCache` configuration variable (see
+linkgit:git-config[1]) than using the `--untracked-cache` option to
+`git update-index` in each repository, especially if you want to do so
+across all repositories you use, because you can set the configuration
+variable to `true` (or `false`) in your `$HOME/.gitconfig` just once
+and have it affect all repositories you touch.
+
+When the `core.untrackedCache` configuration variable is changed, the
+untracked cache is added to or removed from the index the next time a
+command reads the index; while when `--[no-|force-]untracked-cache`
+are used, the untracked cache is immediately added to or removed from
+the index.
+
+Before 2.17, the untracked cache had a bug where replacing a directory
+with a symlink to another directory could cause it to incorrectly show
+files tracked by git as untracked. See the "status: add a failing test
+showing a core.untrackedCache bug" commit to git.git. A workaround for
+that is (and this might work for other undiscovered bugs in the
+future):
+
+----------------
+$ git -c core.untrackedCache=false status
+----------------
+
+This bug has also been shown to affect non-symlink cases of replacing
+a directory with a file when it comes to the internal structures of
+the untracked cache, but no case has been reported where this resulted in
+wrong "git status" output.
+
+There are also cases where existing indexes written by git versions
+before 2.17 will reference directories that don't exist anymore,
+potentially causing many "could not open directory" warnings to be
+printed on "git status". These are new warnings for existing issues
+that were previously silently discarded.
+
+As with the bug described above the solution is to one-off do a "git
+status" run with `core.untrackedCache=false` to flush out the leftover
+bad data.
+
+FILE SYSTEM MONITOR
+-------------------
+
+This feature is intended to speed up git operations for repos that have
+large working directories.
+
+It enables git to work together with a file system monitor (see the
+"fsmonitor-watchman" section of linkgit:githooks[5]) that can
+inform it as to what files have been modified. This enables git to avoid
+having to lstat() every file to find modified files.
+
+When used in conjunction with the untracked cache, it can further improve
+performance by avoiding the cost of scanning the entire working directory
+looking for new files.
+
+If you want to enable (or disable) this feature, it is easier to use
+the `core.fsmonitor` configuration variable (see
+linkgit:git-config[1]) than using the `--fsmonitor` option to
+`git update-index` in each repository, especially if you want to do so
+across all repositories you use, because you can set the configuration
+variable in your `$HOME/.gitconfig` just once and have it affect all
+repositories you touch.
+
+When the `core.fsmonitor` configuration variable is changed, the
+file system monitor is added to or removed from the index the next time
+a command reads the index. When `--[no-]fsmonitor` are used, the file
+system monitor is immediately added to or removed from the index.
+
+CONFIGURATION
+-------------
+
+The command honors `core.filemode` configuration variable.  If
+your repository is on a filesystem whose executable bits are
+unreliable, this should be set to 'false' (see linkgit:git-config[1]).
+This causes the command to ignore differences in file modes recorded
+in the index and the file mode on the filesystem if they differ only on
+executable bit.   On such an unfortunate filesystem, you may
+need to use 'git update-index --chmod='.
+
+Quite similarly, if `core.symlinks` configuration variable is set
+to 'false' (see linkgit:git-config[1]), symbolic links are checked out
+as plain files, and this command does not modify a recorded file mode
+from symbolic link to regular file.
+
+The command looks at `core.ignorestat` configuration variable.  See
+'Using "assume unchanged" bit' section above.
+
+The command also looks at `core.trustctime` configuration variable.
+It can be useful when the inode change time is regularly modified by
+something outside Git (file system crawlers and backup systems use
+ctime for marking files processed) (see linkgit:git-config[1]).
+
+The untracked cache extension can be enabled by the
+`core.untrackedCache` configuration variable (see
+linkgit:git-config[1]).
+
+SEE ALSO
+--------
+linkgit:git-config[1],
+linkgit:git-add[1],
+linkgit:git-ls-files[1]
+
+GIT
+---
+Part of the linkgit:git[1] suite