How can I get/list/see all the descendants of a commit with git (or gitk)?

Question

If you use gitk --all, you can see all the commits of your repo, from all branches. I want something like that except only the descendants of a given commit.

Answer 1

I think this might do what you want. All commits in all branches, that have A as ancestor:

gitk --all --ancestry-path A..

Answer 2

In short:

git log --all BRANCH~1..

In detail, with examples: This is the complete tree of a repository I just created:

$ git log --graph --oneline --decorate --all
* e3972be (HEAD, a) a-6
* 2707d79 a-5
* cdea9a7 a-4
| * 65b716e (c) c-5
| * ebe2a0e c-4
|/  
| * 2ed9abe (b) b-4
|/  
* ace558e (master) 3
* 20db61f 2
* 3923af1 1

Aside from --all, another thing is obvious: master -> HEAD:

$ git log --graph --oneline --decorate master..
* e3972be (HEAD, a) a-6
* 2707d79 a-5
* cdea9a7 a-4

So I tried combining them, and it almost got me what we wanted:

$ git log --graph --oneline --decorate --all master..
* e3972be (HEAD, a) a-6
* 2707d79 a-5
* cdea9a7 a-4
* 65b716e (c) c-5
* ebe2a0e c-4
* 2ed9abe (b) b-4

But unfortunately, this doesn't show the relationship between the branches, since the branch we're asking about was omitted. So we have to use log from the parent of master like so:

$ git log --graph --oneline --decorate --all master~1..
* e3972be (HEAD, a) a-6
* 2707d79 a-5
* cdea9a7 a-4
| * 65b716e (c) c-5
| * ebe2a0e c-4
|/  
| * 2ed9abe (b) b-4
|/  
* ace558e (master) 3

Ta-da! (I don't know if this simply didn't work in the past, but just in case: I'm on git version 1.7.1)

EDIT 2017-11-17 - Thanks to STW for actually showing the problem with this: Independent trees would mess this up. Commits that are entirely independent of master would be included in this output. Starting from a copy of the above repo, this is what my last command would output:

$ git checkout --orphan z
Switched to a new branch 'z'
$ git commit --allow-empty -m'z-1'
[z (root-commit) bc0c0bb] z-1
$ git commit --allow-empty -m'z-2'
[z 1183713] z-2

$ git log --graph --oneline --decorate --all master~1..
* 1183713 (HEAD -> z) z-2
* bc0c0bb z-1
* 6069f73 (a) a-6
* 654d106 a-5
* a218c59 a-4
| * 338432a (c) c-5
| * 2115318 c-4
|/  
| * 43a34dc (b) b-4
|/  
* ce05471 (master) 3

The z branch, being created as an orphan, has no common history with master, so z-1 and z-2 should have been excluded but were not. This is what --ancestry-path is for, I now get. Including it will exclude branch z:

$ git log --graph --oneline --decorate --all --ancestry-path master~1..
* 6069f73 (a) a-6
* 654d106 a-5
* a218c59 a-4
| * 338432a (c) c-5
| * 2115318 c-4
|/  
| * 43a34dc (b) b-4
|/  
* ce05471 (master) 3

For completeness, even given that it already had --ancestry-path, the current top answer does not show the branch relationship correctly because it excludes the commit on master itself:

$ git log --graph --oneline --decorate --all --ancestry-path master..
* 6069f73 (a) a-6
* 654d106 a-5
* a218c59 a-4
* 338432a (c) c-5
* 2115318 c-4
* 43a34dc (b) b-4