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+SPECIFYING REVISIONS
+--------------------
+
+A revision parameter '<rev>' typically, but not necessarily, names a
+commit object. It uses what is called an 'extended SHA1'
+syntax. Here are various ways to spell object names. The
+ones listed near the end of this list name trees and
+blobs contained in a commit.
+
+'<sha1>', e.g. 'dae86e1950b1277e545cee180551750029cfe735', 'dae86e'::
+ The full SHA1 object name (40-byte hexadecimal string), or
+ a leading substring that is unique within the repository.
+ E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
+ name the same commit object if there is no other object in
+ your repository whose object name starts with dae86e.
+
+'<describeOutput>', e.g. 'v1.7.4.2-679-g3bee7fb'::
+ Output from `git describe`; i.e. a closest tag, optionally
+ followed by a dash and a number of commits, followed by a dash, a
+ 'g', and an abbreviated object name.
+
+'<refname>', e.g. 'master', 'heads/master', 'refs/heads/master'::
+ A symbolic ref name. E.g. 'master' typically means the commit
+ object referenced by 'refs/heads/master'. If you
+ happen to have both 'heads/master' and 'tags/master', you can
+ explicitly say 'heads/master' to tell git which one you mean.
+ When ambiguous, a '<name>' is disambiguated by taking the
+ first match in the following rules:
+
+ . If '$GIT_DIR/<name>' exists, that is what you mean (this is usually
+ useful only for 'HEAD', 'FETCH_HEAD', 'ORIG_HEAD', 'MERGE_HEAD'
+ and 'CHERRY_PICK_HEAD');
+
+ . otherwise, 'refs/<name>' if it exists;
+
+ . otherwise, 'refs/tags/<refname>' if it exists;
+
+ . otherwise, 'refs/heads/<name>' if it exists;
+
+ . otherwise, 'refs/remotes/<name>' if it exists;
+
+ . otherwise, 'refs/remotes/<name>/HEAD' if it exists.
++
+'HEAD' names the commit on which you based the changes in the working tree.
+'FETCH_HEAD' records the branch which you fetched from a remote repository
+with your last `git fetch` invocation.
+'ORIG_HEAD' is created by commands that move your 'HEAD' in a drastic
+way, to record the position of the 'HEAD' before their operation, so that
+you can easily change the tip of the branch back to the state before you ran
+them.
+'MERGE_HEAD' records the commit(s) which you are merging into your branch
+when you run `git merge`.
+'CHERRY_PICK_HEAD' records the commit which you are cherry-picking
+when you run `git cherry-pick`.
++
+Note that any of the 'refs/*' cases above may come either from
+the '$GIT_DIR/refs' directory or from the '$GIT_DIR/packed-refs' file.
+
+'<refname>@\{<date>\}', e.g. 'master@\{yesterday\}', 'HEAD@\{5 minutes ago\}'::
+ A ref followed by the suffix '@' with a date specification
+ enclosed in a brace
+ pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
+ second ago\}' or '\{1979-02-26 18:30:00\}') specifies the value
+ of the ref at a prior point in time. This suffix may only be
+ used immediately following a ref name and the ref must have an
+ existing log ('$GIT_DIR/logs/<ref>'). Note that this looks up the state
+ of your *local* ref at a given time; e.g., what was in your local
+ 'master' branch last week. If you want to look at commits made during
+ certain times, see '--since' and '--until'.
+
+'<refname>@\{<n>\}', e.g. 'master@\{1\}'::
+ A ref followed by the suffix '@' with an ordinal specification
+ enclosed in a brace pair (e.g. '\{1\}', '\{15\}') specifies
+ the n-th prior value of that ref. For example 'master@\{1\}'
+ is the immediate prior value of 'master' while 'master@\{5\}'
+ is the 5th prior value of 'master'. This suffix may only be used
+ immediately following a ref name and the ref must have an existing
+ log ('$GIT_DIR/logs/<refname>').
+
+'@\{<n>\}', e.g. '@\{1\}'::
+ You can use the '@' construct with an empty ref part to get at a
+ reflog entry of the current branch. For example, if you are on
+ branch 'blabla' then '@\{1\}' means the same as 'blabla@\{1\}'.
+
+'@\{-<n>\}', e.g. '@\{-1\}'::
+ The construct '@\{-<n>\}' means the <n>th branch checked out
+ before the current one.
+
+'<refname>@\{upstream\}', e.g. 'master@\{upstream\}', '@\{u\}'::
+ The suffix '@\{upstream\}' to a ref (short form '<refname>@\{u\}') refers to
+ the branch the ref is set to build on top of. A missing ref defaults
+ to the current branch.
+
+'<rev>{caret}', e.g. 'HEAD{caret}, v1.5.1{caret}0'::
+ A suffix '{caret}' to a revision parameter means the first parent of
+ that commit object. '{caret}<n>' means the <n>th parent (i.e.
+ '<rev>{caret}'
+ is equivalent to '<rev>{caret}1'). As a special rule,
+ '<rev>{caret}0' means the commit itself and is used when '<rev>' is the
+ object name of a tag object that refers to a commit object.
+
+'<rev>{tilde}<n>', e.g. 'master{tilde}3'::
+ A suffix '{tilde}<n>' to a revision parameter means the commit
+ object that is the <n>th generation ancestor of the named
+ commit object, following only the first parents. I.e. '<rev>{tilde}3' is
+ equivalent to '<rev>{caret}{caret}{caret}' which is equivalent to
+ '<rev>{caret}1{caret}1{caret}1'. See below for an illustration of
+ the usage of this form.
+
+'<rev>{caret}\{<type>\}', e.g. 'v0.99.8{caret}\{commit\}'::
+ A suffix '{caret}' followed by an object type name enclosed in
+ brace pair means the object
+ could be a tag, and dereference the tag recursively until an
+ object of that type is found or the object cannot be
+ dereferenced anymore (in which case, barf). '<rev>{caret}0'
+ is a short-hand for '<rev>{caret}\{commit\}'.
+
+'<rev>{caret}\{\}', e.g. 'v0.99.8{caret}\{\}'::
+ A suffix '{caret}' followed by an empty brace pair
+ means the object could be a tag,
+ and dereference the tag recursively until a non-tag object is
+ found.
+
+'<rev>{caret}\{/<text>\}', e.g. 'HEAD^{/fix nasty bug}'::
+ A suffix '{caret}' to a revision parameter, followed by a brace
+ pair that contains a text led by a slash,
+ is the same as the ':/fix nasty bug' syntax below except that
+ it returns the youngest matching commit which is reachable from
+ the '<rev>' before '{caret}'.
+
+':/<text>', e.g. ':/fix nasty bug'::
+ A colon, followed by a slash, followed by a text, names
+ a commit whose commit message matches the specified regular expression.
+ This name returns the youngest matching commit which is
+ reachable from any ref. If the commit message starts with a
+ '!' you have to repeat that; the special sequence ':/!',
+ followed by something else than '!', is reserved for now.
+ The regular expression can match any part of the commit message. To
+ match messages starting with a string, one can use e.g. ':/^foo'.
+
+'<rev>:<path>', e.g. 'HEAD:README', ':README', 'master:./README'::
+ A suffix ':' followed by a path names the blob or tree
+ at the given path in the tree-ish object named by the part
+ before the colon.
+ ':path' (with an empty part before the colon)
+ is a special case of the syntax described next: content
+ recorded in the index at the given path.
+ A path starting with './' or '../' is relative to the current working directory.
+ The given path will be converted to be relative to the working tree's root directory.
+ This is most useful to address a blob or tree from a commit or tree that has
+ the same tree structure as the working tree.
+
+':<n>:<path>', e.g. ':0:README', ':README'::
+ A colon, optionally followed by a stage number (0 to 3) and a
+ colon, followed by a path, names a blob object in the
+ index at the given path. A missing stage number (and the colon
+ that follows it) names a stage 0 entry. During a merge, stage
+ 1 is the common ancestor, stage 2 is the target branch's version
+ (typically the current branch), and stage 3 is the version from
+ the branch which is being merged.
+
+Here is an illustration, by Jon Loeliger. Both commit nodes B
+and C are parents of commit node A. Parent commits are ordered
+left-to-right.
+
+........................................
+G H I J
+ \ / \ /
+ D E F
+ \ | / \
+ \ | / |
+ \|/ |
+ B C
+ \ /
+ \ /
+ A
+........................................
+
+ A = = A^0
+ B = A^ = A^1 = A~1
+ C = A^2 = A^2
+ D = A^^ = A^1^1 = A~2
+ E = B^2 = A^^2
+ F = B^3 = A^^3
+ G = A^^^ = A^1^1^1 = A~3
+ H = D^2 = B^^2 = A^^^2 = A~2^2
+ I = F^ = B^3^ = A^^3^
+ J = F^2 = B^3^2 = A^^3^2
+
+
+SPECIFYING RANGES
+-----------------
+
+History traversing commands such as `git log` operate on a set
+of commits, not just a single commit. To these commands,
+specifying a single revision with the notation described in the
+previous section means the set of commits reachable from that
+commit, following the commit ancestry chain.
+
+To exclude commits reachable from a commit, a prefix '{caret}'
+notation is used. E.g. '{caret}r1 r2' means commits reachable
+from 'r2' but exclude the ones reachable from 'r1'.
+
+This set operation appears so often that there is a shorthand
+for it. When you have two commits 'r1' and 'r2' (named according
+to the syntax explained in SPECIFYING REVISIONS above), you can ask
+for commits that are reachable from r2 excluding those that are reachable
+from r1 by '{caret}r1 r2' and it can be written as 'r1..r2'.
+
+A similar notation 'r1\...r2' is called symmetric difference
+of 'r1' and 'r2' and is defined as
+'r1 r2 --not $(git merge-base --all r1 r2)'.
+It is the set of commits that are reachable from either one of
+'r1' or 'r2' but not from both.
+
+Two other shorthands for naming a set that is formed by a commit
+and its parent commits exist. The 'r1{caret}@' notation means all
+parents of 'r1'. 'r1{caret}!' includes commit 'r1' but excludes
+all of its parents.
+
+Here are a handful of examples:
+
+ D G H D
+ D F G H I J D F
+ ^G D H D
+ ^D B E I J F B
+ B...C G H D E B C
+ ^D B C E I J F B C
+ C^@ I J F
+ F^! D G H D F