| SPECIFYING REVISIONS |
| -------------------- |
| |
| A revision parameter typically, but not necessarily, names a |
| commit object. They use what is called an 'extended SHA1' |
| syntax. Here are various ways to spell object names. The |
| ones listed near the end of this list are to name trees and |
| blobs contained in a commit. |
| |
| * The full SHA1 object name (40-byte hexadecimal string), or |
| a substring of such that is unique within the repository. |
| E.g. dae86e1950b1277e545cee180551750029cfe735 and dae86e both |
| name the same commit object if there are no other object in |
| your repository whose object name starts with dae86e. |
| |
| * An 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. |
| |
| * 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 `$GIT_DIR/<name>` exists, that is what you mean (this is usually |
| useful only for `HEAD`, `FETCH_HEAD`, `ORIG_HEAD` and `MERGE_HEAD`); |
| |
| . otherwise, `refs/<name>` if exists; |
| |
| . otherwise, `refs/tags/<name>` if exists; |
| |
| . otherwise, `refs/heads/<name>` if exists; |
| |
| . otherwise, `refs/remotes/<name>` if exists; |
| |
| . otherwise, `refs/remotes/<name>/HEAD` if exists. |
| + |
| HEAD names the commit your changes in the working tree is based on. |
| FETCH_HEAD records the branch you fetched from a remote repository |
| with your last 'git fetch' invocation. |
| ORIG_HEAD is created by commands that moves your HEAD in a drastic |
| way, to record the position of the HEAD before their operation, so that |
| you can change the tip of the branch back to the state before you ran |
| them easily. |
| MERGE_HEAD records the commit(s) you are merging into your branch |
| when you run 'git merge'. |
| + |
| Note that any of the `refs/*` cases above may come either from |
| the `$GIT_DIR/refs` directory or from the `$GIT_DIR/packed-refs` file. |
| |
| * A ref followed by the suffix '@' with a date specification |
| enclosed in a brace |
| pair (e.g. '\{yesterday\}', '\{1 month 2 weeks 3 days 1 hour 1 |
| second ago\}' or '\{1979-02-26 18:30:00\}') to specify the value |
| of the ref at a prior point in time. This suffix may only be |
| used immediately following a ref name and the ref must have an |
| existing log ($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`. |
| |
| * A ref followed by the suffix '@' with an ordinal specification |
| enclosed in a brace pair (e.g. '\{1\}', '\{15\}') to specify |
| 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/<ref>). |
| |
| * You can use the '@' construct with an empty ref part to get at a |
| reflog of the current branch. For example, if you are on the |
| branch 'blabla', then '@\{1\}' means the same as 'blabla@\{1\}'. |
| |
| * The special construct '@\{-<n>\}' means the <n>th branch checked out |
| before the current one. |
| |
| * The suffix '@\{upstream\}' to a ref (short form 'ref@\{u\}') refers to |
| the branch the ref is set to build on top of. Missing ref defaults |
| to the current branch. |
| |
| * A suffix '{caret}' to a revision parameter (e.g. 'HEAD{caret}') 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. |
| |
| * A suffix '{tilde}<n>' to a revision parameter means the commit |
| object that is the <n>th generation grand-parent of the named |
| commit object, following only the first parent. I.e. rev~3 is |
| equivalent to rev{caret}{caret}{caret} which is equivalent to |
| rev{caret}1{caret}1{caret}1. See below for a illustration of |
| the usage of this form. |
| |
| * A suffix '{caret}' followed by an object type name enclosed in |
| brace pair (e.g. `v0.99.8{caret}\{commit\}`) 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` |
| introduced earlier is a short-hand for `rev{caret}\{commit\}`. |
| |
| * A suffix '{caret}' followed by an empty brace pair |
| (e.g. `v0.99.8{caret}\{\}`) means the object could be a tag, |
| and dereference the tag recursively until a non-tag object is |
| found. |
| |
| * A colon, followed by a slash, followed by a text (e.g. `:/fix nasty bug`): this 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`. |
| |
| * A suffix ':' followed by a path (e.g. `HEAD:README`); this 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, e.g. `:README`) |
| is a special case of the syntax described next: content |
| recorded in the index at the given path. |
| |
| * A colon, optionally followed by a stage number (0 to 3) and a |
| colon, followed by a path (e.g. `:0:README`); this names a blob object in the |
| index at the given path. Missing stage number (and the colon |
| that follows it, e.g. `:README`) 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 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 |