Documentation / gitcli.txton commit merge-options.txt: clarify meaning of various ff-related options (27fd1e4)
   1gitcli(7)
   2=========
   3
   4NAME
   5----
   6gitcli - Git command-line interface and conventions
   7
   8SYNOPSIS
   9--------
  10gitcli
  11
  12
  13DESCRIPTION
  14-----------
  15
  16This manual describes the convention used throughout Git CLI.
  17
  18Many commands take revisions (most often "commits", but sometimes
  19"tree-ish", depending on the context and command) and paths as their
  20arguments.  Here are the rules:
  21
  22 * Revisions come first and then paths.
  23   E.g. in `git diff v1.0 v2.0 arch/x86 include/asm-x86`,
  24   `v1.0` and `v2.0` are revisions and `arch/x86` and `include/asm-x86`
  25   are paths.
  26
  27 * When an argument can be misunderstood as either a revision or a path,
  28   they can be disambiguated by placing `--` between them.
  29   E.g. `git diff -- HEAD` is, "I have a file called HEAD in my work
  30   tree.  Please show changes between the version I staged in the index
  31   and what I have in the work tree for that file", not "show difference
  32   between the HEAD commit and the work tree as a whole".  You can say
  33   `git diff HEAD --` to ask for the latter.
  34
  35 * Without disambiguating `--`, Git makes a reasonable guess, but errors
  36   out and asking you to disambiguate when ambiguous.  E.g. if you have a
  37   file called HEAD in your work tree, `git diff HEAD` is ambiguous, and
  38   you have to say either `git diff HEAD --` or `git diff -- HEAD` to
  39   disambiguate.
  40+
  41When writing a script that is expected to handle random user-input, it is
  42a good practice to make it explicit which arguments are which by placing
  43disambiguating `--` at appropriate places.
  44
  45 * Many commands allow wildcards in paths, but you need to protect
  46   them from getting globbed by the shell.  These two mean different
  47   things:
  48+
  49--------------------------------
  50$ git checkout -- *.c
  51$ git checkout -- \*.c
  52--------------------------------
  53+
  54The former lets your shell expand the fileglob, and you are asking
  55the dot-C files in your working tree to be overwritten with the version
  56in the index.  The latter passes the `*.c` to Git, and you are asking
  57the paths in the index that match the pattern to be checked out to your
  58working tree.  After running `git add hello.c; rm hello.c`, you will _not_
  59see `hello.c` in your working tree with the former, but with the latter
  60you will.
  61
  62 * Just as the filesystem '.' (period) refers to the current directory,
  63   using a '.' as a repository name in Git (a dot-repository) is a relative
  64   path and means your current repository.
  65
  66Here are the rules regarding the "flags" that you should follow when you are
  67scripting Git:
  68
  69 * it's preferred to use the non-dashed form of Git commands, which means that
  70   you should prefer `git foo` to `git-foo`.
  71
  72 * splitting short options to separate words (prefer `git foo -a -b`
  73   to `git foo -ab`, the latter may not even work).
  74
  75 * when a command-line option takes an argument, use the 'stuck' form.  In
  76   other words, write `git foo -oArg` instead of `git foo -o Arg` for short
  77   options, and `git foo --long-opt=Arg` instead of `git foo --long-opt Arg`
  78   for long options.  An option that takes optional option-argument must be
  79   written in the 'stuck' form.
  80
  81 * when you give a revision parameter to a command, make sure the parameter is
  82   not ambiguous with a name of a file in the work tree.  E.g. do not write
  83   `git log -1 HEAD` but write `git log -1 HEAD --`; the former will not work
  84   if you happen to have a file called `HEAD` in the work tree.
  85
  86 * many commands allow a long option `--option` to be abbreviated
  87   only to their unique prefix (e.g. if there is no other option
  88   whose name begins with `opt`, you may be able to spell `--opt` to
  89   invoke the `--option` flag), but you should fully spell them out
  90   when writing your scripts; later versions of Git may introduce a
  91   new option whose name shares the same prefix, e.g. `--optimize`,
  92   to make a short prefix that used to be unique no longer unique.
  93
  94
  95ENHANCED OPTION PARSER
  96----------------------
  97From the Git 1.5.4 series and further, many Git commands (not all of them at the
  98time of the writing though) come with an enhanced option parser.
  99
 100Here is a list of the facilities provided by this option parser.
 101
 102
 103Magic Options
 104~~~~~~~~~~~~~
 105Commands which have the enhanced option parser activated all understand a
 106couple of magic command-line options:
 107
 108-h::
 109        gives a pretty printed usage of the command.
 110+
 111---------------------------------------------
 112$ git describe -h
 113usage: git describe [<options>] <commit-ish>*
 114   or: git describe [<options>] --dirty
 115
 116    --contains            find the tag that comes after the commit
 117    --debug               debug search strategy on stderr
 118    --all                 use any ref
 119    --tags                use any tag, even unannotated
 120    --long                always use long format
 121    --abbrev[=<n>]        use <n> digits to display SHA-1s
 122---------------------------------------------
 123
 124--help-all::
 125        Some Git commands take options that are only used for plumbing or that
 126        are deprecated, and such options are hidden from the default usage. This
 127        option gives the full list of options.
 128
 129
 130Negating options
 131~~~~~~~~~~~~~~~~
 132Options with long option names can be negated by prefixing `--no-`. For
 133example, `git branch` has the option `--track` which is 'on' by default. You
 134can use `--no-track` to override that behaviour. The same goes for `--color`
 135and `--no-color`.
 136
 137
 138Aggregating short options
 139~~~~~~~~~~~~~~~~~~~~~~~~~
 140Commands that support the enhanced option parser allow you to aggregate short
 141options. This means that you can for example use `git rm -rf` or
 142`git clean -fdx`.
 143
 144
 145Abbreviating long options
 146~~~~~~~~~~~~~~~~~~~~~~~~~
 147Commands that support the enhanced option parser accepts unique
 148prefix of a long option as if it is fully spelled out, but use this
 149with a caution.  For example, `git commit --amen` behaves as if you
 150typed `git commit --amend`, but that is true only until a later version
 151of Git introduces another option that shares the same prefix,
 152e.g. `git commit --amenity` option.
 153
 154
 155Separating argument from the option
 156~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 157You can write the mandatory option parameter to an option as a separate
 158word on the command line.  That means that all the following uses work:
 159
 160----------------------------
 161$ git foo --long-opt=Arg
 162$ git foo --long-opt Arg
 163$ git foo -oArg
 164$ git foo -o Arg
 165----------------------------
 166
 167However, this is *NOT* allowed for switches with an optional value, where the
 168'stuck' form must be used:
 169----------------------------
 170$ git describe --abbrev HEAD     # correct
 171$ git describe --abbrev=10 HEAD  # correct
 172$ git describe --abbrev 10 HEAD  # NOT WHAT YOU MEANT
 173----------------------------
 174
 175
 176NOTES ON FREQUENTLY CONFUSED OPTIONS
 177------------------------------------
 178
 179Many commands that can work on files in the working tree
 180and/or in the index can take `--cached` and/or `--index`
 181options.  Sometimes people incorrectly think that, because
 182the index was originally called cache, these two are
 183synonyms.  They are *not* -- these two options mean very
 184different things.
 185
 186 * The `--cached` option is used to ask a command that
 187   usually works on files in the working tree to *only* work
 188   with the index.  For example, `git grep`, when used
 189   without a commit to specify from which commit to look for
 190   strings in, usually works on files in the working tree,
 191   but with the `--cached` option, it looks for strings in
 192   the index.
 193
 194 * The `--index` option is used to ask a command that
 195   usually works on files in the working tree to *also*
 196   affect the index.  For example, `git stash apply` usually
 197   merges changes recorded in a stash entry to the working tree,
 198   but with the `--index` option, it also merges changes to
 199   the index as well.
 200
 201`git apply` command can be used with `--cached` and
 202`--index` (but not at the same time).  Usually the command
 203only affects the files in the working tree, but with
 204`--index`, it patches both the files and their index
 205entries, and with `--cached`, it modifies only the index
 206entries.
 207
 208See also http://marc.info/?l=git&m=116563135620359 and
 209http://marc.info/?l=git&m=119150393620273 for further
 210information.
 211
 212GIT
 213---
 214Part of the linkgit:git[1] suite