David Greaves | 2cf565c | 2005-05-10 22:32:30 +0100 | [diff] [blame] | 1 | git-merge-base(1) |
| 2 | ================= |
David Greaves | 2cf565c | 2005-05-10 22:32:30 +0100 | [diff] [blame] | 3 | |
| 4 | NAME |
| 5 | ---- |
Junio C Hamano | c3f0baa | 2007-01-18 15:53:37 -0800 | [diff] [blame] | 6 | git-merge-base - Find as good common ancestors as possible for a merge |
David Greaves | 2cf565c | 2005-05-10 22:32:30 +0100 | [diff] [blame] | 7 | |
| 8 | |
| 9 | SYNOPSIS |
| 10 | -------- |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 11 | 'git merge-base' [--all] <commit> <commit>... |
David Greaves | 2cf565c | 2005-05-10 22:32:30 +0100 | [diff] [blame] | 12 | |
| 13 | DESCRIPTION |
| 14 | ----------- |
Fredrik Kuivinen | 2aa8396 | 2006-05-16 07:58:15 +0200 | [diff] [blame] | 15 | |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 16 | 'git-merge-base' finds best common ancestor(s) between two commits to use |
| 17 | in a three-way merge. One common ancestor is 'better' than another common |
| 18 | ancestor if the latter is an ancestor of the former. A common ancestor |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 19 | that does not have any better common ancestor is a 'best common |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 20 | ancestor', i.e. a 'merge base'. Note that there can be more than one |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 21 | merge base for a pair of commits. |
Fredrik Kuivinen | 2aa8396 | 2006-05-16 07:58:15 +0200 | [diff] [blame] | 22 | |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 23 | Among the two commits to compute the merge base from, one is specified by |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 24 | the first commit argument on the command line; the other commit is a |
| 25 | (possibly hypothetical) commit that is a merge across all the remaining |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 26 | commits on the command line. As the most common special case, specifying only |
| 27 | two commits on the command line means computing the merge base between |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 28 | the given two commits. |
David Greaves | 2cf565c | 2005-05-10 22:32:30 +0100 | [diff] [blame] | 29 | |
Fredrik Kuivinen | 2aa8396 | 2006-05-16 07:58:15 +0200 | [diff] [blame] | 30 | OPTIONS |
| 31 | ------- |
| 32 | --all:: |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 33 | Output all merge bases for the commits, instead of just one. |
| 34 | |
| 35 | DISCUSSION |
| 36 | ---------- |
| 37 | |
| 38 | Given two commits 'A' and 'B', `git merge-base A B` will output a commit |
| 39 | which is reachable from both 'A' and 'B' through the parent relationship. |
| 40 | |
| 41 | For example, with this topology: |
| 42 | |
| 43 | o---o---o---B |
| 44 | / |
| 45 | ---o---1---o---o---o---A |
| 46 | |
| 47 | the merge base between 'A' and 'B' is '1'. |
| 48 | |
| 49 | Given three commits 'A', 'B' and 'C', `git merge-base A B C` will compute the |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 50 | merge base between 'A' and a hypothetical commit 'M', which is a merge |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 51 | between 'B' and 'C'. For example, with this topology: |
| 52 | |
| 53 | o---o---o---o---C |
| 54 | / |
| 55 | / o---o---o---B |
| 56 | / / |
| 57 | ---2---1---o---o---o---A |
| 58 | |
| 59 | the result of `git merge-base A B C` is '1'. This is because the |
| 60 | equivalent topology with a merge commit 'M' between 'B' and 'C' is: |
| 61 | |
| 62 | |
| 63 | o---o---o---o---o |
| 64 | / \ |
| 65 | / o---o---o---o---M |
| 66 | / / |
| 67 | ---2---1---o---o---o---A |
| 68 | |
| 69 | and the result of `git merge-base A M` is '1'. Commit '2' is also a |
| 70 | common ancestor between 'A' and 'M', but '1' is a better common ancestor, |
| 71 | because '2' is an ancestor of '1'. Hence, '2' is not a merge base. |
| 72 | |
| 73 | When the history involves criss-cross merges, there can be more than one |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 74 | 'best' common ancestor for two commits. For example, with this topology: |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 75 | |
| 76 | ---1---o---A |
| 77 | \ / |
| 78 | X |
| 79 | / \ |
| 80 | ---2---o---o---B |
| 81 | |
Ralf Wildenhues | 29b802a | 2008-12-09 07:23:51 +0100 | [diff] [blame] | 82 | both '1' and '2' are merge-bases of A and B. Neither one is better than |
| 83 | the other (both are 'best' merge bases). When the `--all` option is not given, |
Junio C Hamano | 99f1c04 | 2008-07-30 07:04:43 +0200 | [diff] [blame] | 84 | it is unspecified which best one is output. |
David Greaves | 2cf565c | 2005-05-10 22:32:30 +0100 | [diff] [blame] | 85 | |
| 86 | Author |
| 87 | ------ |
| 88 | Written by Linus Torvalds <torvalds@osdl.org> |
| 89 | |
| 90 | Documentation |
| 91 | -------------- |
| 92 | Documentation by David Greaves, Junio C Hamano and the git-list <git@vger.kernel.org>. |
| 93 | |
| 94 | GIT |
| 95 | --- |
Christian Couder | 9e1f0a8 | 2008-06-06 09:07:32 +0200 | [diff] [blame] | 96 | Part of the linkgit:git[1] suite |