41cd7974b0
* nd/oneline-sha1-name-from-specific-ref:
get_sha1: handle special case $commit^{/}
get_sha1: support $commit^{/regex} syntax
get_sha1_oneline: make callers prepare the commit list to traverse
get_sha1_oneline: fix lifespan rule of temp_commit_buffer variable
212 lines
8.8 KiB
Plaintext
212 lines
8.8 KiB
Plaintext
SPECIFYING REVISIONS
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--------------------
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A revision parameter typically, but not necessarily, names a
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commit object. They use what is called an 'extended SHA1'
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syntax. Here are various ways to spell object names. The
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ones listed near the end of this list are to name trees and
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blobs contained in a commit.
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* The full SHA1 object name (40-byte hexadecimal string), or
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a substring of such that is unique within the repository.
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E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both
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name the same commit object if there are no other object in
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your repository whose object name starts with dae86e.
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* An output from 'git describe'; i.e. a closest tag, optionally
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followed by a dash and a number of commits, followed by a dash, a
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`g`, and an abbreviated object name.
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* A symbolic ref name. E.g. 'master' typically means the commit
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object referenced by refs/heads/master. If you
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happen to have both heads/master and tags/master, you can
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explicitly say 'heads/master' to tell git which one you mean.
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When ambiguous, a `<name>` is disambiguated by taking the
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first match in the following rules:
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. if `$GIT_DIR/<name>` exists, that is what you mean (this is usually
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useful only for `HEAD`, `FETCH_HEAD`, `ORIG_HEAD` and `MERGE_HEAD`);
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. otherwise, `refs/<name>` if exists;
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. otherwise, `refs/tags/<name>` if exists;
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. otherwise, `refs/heads/<name>` if exists;
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. otherwise, `refs/remotes/<name>` if exists;
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. otherwise, `refs/remotes/<name>/HEAD` if exists.
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+
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HEAD names the commit your changes in the working tree is based on.
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FETCH_HEAD records the branch you fetched from a remote repository
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with your last 'git fetch' invocation.
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ORIG_HEAD is created by commands that moves your HEAD in a drastic
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way, to record the position of the HEAD before their operation, so that
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you can change the tip of the branch back to the state before you ran
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them easily.
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MERGE_HEAD records the commit(s) you are merging into your branch
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when you run 'git merge'.
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+
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Note that any of the `refs/*` cases above may come either from
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the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file.
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* A ref followed by the suffix '@' with a date specification
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enclosed in a brace
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pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1
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second ago\}' or '\{1979-02-26 18:30:00\}') to specify the value
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of the ref at a prior point in time. This suffix may only be
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used immediately following a ref name and the ref must have an
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existing log ($GIT_DIR/logs/<ref>). Note that this looks up the state
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of your *local* ref at a given time; e.g., what was in your local
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`master` branch last week. If you want to look at commits made during
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certain times, see `--since` and `--until`.
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* A ref followed by the suffix '@' with an ordinal specification
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enclosed in a brace pair (e.g. '\{1\}', '\{15\}') to specify
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the n-th prior value of that ref. For example 'master@\{1\}'
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is the immediate prior value of 'master' while 'master@\{5\}'
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is the 5th prior value of 'master'. This suffix may only be used
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immediately following a ref name and the ref must have an existing
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log ($GIT_DIR/logs/<ref>).
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* You can use the '@' construct with an empty ref part to get at a
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reflog of the current branch. For example, if you are on the
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branch 'blabla', then '@\{1\}' means the same as 'blabla@\{1\}'.
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* The special construct '@\{-<n>\}' means the <n>th branch checked out
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before the current one.
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* The suffix '@\{upstream\}' to a ref (short form 'ref@\{u\}') refers to
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the branch the ref is set to build on top of. Missing ref defaults
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to the current branch.
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* A suffix '{caret}' to a revision parameter (e.g. 'HEAD{caret}') means the first parent of
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that commit object. '{caret}<n>' means the <n>th parent (i.e.
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'rev{caret}'
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is equivalent to 'rev{caret}1'). As a special rule,
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'rev{caret}0' means the commit itself and is used when 'rev' is the
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object name of a tag object that refers to a commit object.
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* A suffix '{tilde}<n>' to a revision parameter means the commit
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object that is the <n>th generation grand-parent of the named
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commit object, following only the first parent. I.e. rev~3 is
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equivalent to rev{caret}{caret}{caret} which is equivalent to
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rev{caret}1{caret}1{caret}1. See below for a illustration of
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the usage of this form.
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* A suffix '{caret}' followed by an object type name enclosed in
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brace pair (e.g. `v0.99.8{caret}\{commit\}`) means the object
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could be a tag, and dereference the tag recursively until an
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object of that type is found or the object cannot be
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dereferenced anymore (in which case, barf). `rev{caret}0`
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introduced earlier is a short-hand for `rev{caret}\{commit\}`.
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* A suffix '{caret}' followed by an empty brace pair
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(e.g. `v0.99.8{caret}\{\}`) means the object could be a tag,
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and dereference the tag recursively until a non-tag object is
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found.
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* A suffix '{caret}' to a revision parameter followed by a brace
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pair that contains a text led by a slash (e.g. `HEAD^{/fix nasty bug}`):
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this is the same as `:/fix nasty bug` syntax below except that
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it returns the youngest matching commit which is reachable from
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the ref before '{caret}'.
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* A colon, followed by a slash, followed by a text (e.g. `:/fix nasty bug`): this names
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a commit whose commit message matches the specified regular expression.
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This name returns the youngest matching commit which is
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reachable from any ref. If the commit message starts with a
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'!', you have to repeat that; the special sequence ':/!',
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followed by something else than '!' is reserved for now.
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The regular expression can match any part of the commit message. To
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match messages starting with a string, one can use e.g. `:/^foo`.
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* A suffix ':' followed by a path (e.g. `HEAD:README`); this names the blob or tree
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at the given path in the tree-ish object named by the part
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before the colon.
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':path' (with an empty part before the colon, e.g. `:README`)
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is a special case of the syntax described next: content
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recorded in the index at the given path.
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A path starting with './' or '../' is relative to current working directory.
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The given path will be converted to be relative to working tree's root directory.
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This is most useful to address a blob or tree from a commit or tree that has
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the same tree structure with the working tree.
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* A colon, optionally followed by a stage number (0 to 3) and a
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colon, followed by a path (e.g. `:0:README`); this names a blob object in the
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index at the given path. Missing stage number (and the colon
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that follows it, e.g. `:README`) names a stage 0 entry. During a merge, stage
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1 is the common ancestor, stage 2 is the target branch's version
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(typically the current branch), and stage 3 is the version from
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the branch being merged.
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Here is an illustration, by Jon Loeliger. Both commit nodes B
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and C are parents of commit node A. Parent commits are ordered
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left-to-right.
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........................................
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G H I J
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\ / \ /
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D E F
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\ | / \
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\ | / |
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\|/ |
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B C
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\ /
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\ /
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A
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........................................
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A = = A^0
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B = A^ = A^1 = A~1
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C = A^2 = A^2
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D = A^^ = A^1^1 = A~2
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E = B^2 = A^^2
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F = B^3 = A^^3
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G = A^^^ = A^1^1^1 = A~3
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H = D^2 = B^^2 = A^^^2 = A~2^2
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I = F^ = B^3^ = A^^3^
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J = F^2 = B^3^2 = A^^3^2
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SPECIFYING RANGES
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-----------------
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History traversing commands such as 'git log' operate on a set
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of commits, not just a single commit. To these commands,
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specifying a single revision with the notation described in the
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previous section means the set of commits reachable from that
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commit, following the commit ancestry chain.
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To exclude commits reachable from a commit, a prefix `{caret}`
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notation is used. E.g. `{caret}r1 r2` means commits reachable
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from `r2` but exclude the ones reachable from `r1`.
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This set operation appears so often that there is a shorthand
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for it. When you have two commits `r1` and `r2` (named according
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to the syntax explained in SPECIFYING REVISIONS above), you can ask
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for commits that are reachable from r2 excluding those that are reachable
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from r1 by `{caret}r1 r2` and it can be written as `r1..r2`.
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A similar notation `r1\...r2` is called symmetric difference
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of `r1` and `r2` and is defined as
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`r1 r2 --not $(git merge-base --all r1 r2)`.
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It is the set of commits that are reachable from either one of
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`r1` or `r2` but not from both.
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Two other shorthands for naming a set that is formed by a commit
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and its parent commits exist. The `r1{caret}@` notation means all
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parents of `r1`. `r1{caret}!` includes commit `r1` but excludes
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all of its parents.
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Here are a handful of examples:
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D G H D
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D F G H I J D F
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^G D H D
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^D B E I J F B
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B...C G H D E B C
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^D B C E I J F B C
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C^@ I J F
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F^! D G H D F
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