dirstate-tree: Add tree traversal/iteration
Like Python’s, Rust’s iterators are "external" in that they are driven
by a caller who calls a `next` method. This is as opposed to "internal"
iterators who drive themselves and call a callback for each item.
Writing an internal iterator traversing a tree is easy with recursion,
but internal iterators cannot rely on the call stack in that way,
they must save in an explicit object all state that they need to be
preserved across two `next` calls.
This algorithm uses a `Vec` as a stack that contains what would be
local variables on the call stack if we could use recursion.
Differential Revision: https://phab.mercurial-scm.org/D10370
$ heads()
> {
> hg heads --template '{rev}: {desc|firstline|strip} ({branches})\n' "$@"
> }
$ hg init a
$ cd a
$ echo 'root' >root
$ hg add root
$ hg commit -m "Adding root node"
$ heads
0: Adding root node ()
-------
$ heads .
0: Adding root node ()
=======
$ echo 'a' >a
$ hg add a
$ hg branch a
marked working directory as branch a
(branches are permanent and global, did you want a bookmark?)
$ hg commit -m "Adding a branch"
$ heads
1: Adding a branch (a)
0: Adding root node ()
-------
$ heads .
1: Adding a branch (a)
=======
$ hg update -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo 'b' >b
$ hg add b
$ hg branch b
marked working directory as branch b
$ hg commit -m "Adding b branch"
$ heads
2: Adding b branch (b)
1: Adding a branch (a)
0: Adding root node ()
-------
$ heads .
2: Adding b branch (b)
=======
$ echo 'bh1' >bh1
$ hg add bh1
$ hg commit -m "Adding b branch head 1"
$ heads
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
$ heads .
3: Adding b branch head 1 (b)
=======
$ hg update -C 2
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo 'bh2' >bh2
$ hg add bh2
$ hg commit -m "Adding b branch head 2"
created new head
$ heads
4: Adding b branch head 2 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
$ heads .
4: Adding b branch head 2 (b)
3: Adding b branch head 1 (b)
=======
$ hg update -C 2
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo 'bh3' >bh3
$ hg add bh3
$ hg commit -m "Adding b branch head 3"
created new head
$ heads
5: Adding b branch head 3 (b)
4: Adding b branch head 2 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
$ heads .
5: Adding b branch head 3 (b)
4: Adding b branch head 2 (b)
3: Adding b branch head 1 (b)
=======
$ hg merge 4
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg commit -m "Merging b branch head 2 and b branch head 3"
$ heads
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
$ heads .
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
=======
$ echo 'c' >c
$ hg add c
$ hg branch c
marked working directory as branch c
$ hg commit -m "Adding c branch"
$ heads
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
$ heads .
7: Adding c branch (c)
=======
$ heads -r 3 .
no open branch heads found on branches c (started at 3)
[1]
$ heads -r 2 .
7: Adding c branch (c)
-------
$ hg update -C 4
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
-------
$ heads -r 3 .
3: Adding b branch head 1 (b)
-------
$ heads -r 2 .
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
$ heads -r 7 .
no open branch heads found on branches b (started at 7)
[1]
=======
$ for i in 0 1 2 3 4 5 6 7; do
> hg update -C "$i"
> heads
> echo '-------'
> heads .
> echo '-------'
> done
0 files updated, 0 files merged, 2 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
0: Adding root node ()
-------
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
1: Adding a branch (a)
-------
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
1 files updated, 0 files merged, 1 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
-------
7: Adding c branch (c)
-------
=======
$ for i in a b c z; do
> heads "$i"
> echo '-------'
> done
1: Adding a branch (a)
-------
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
-------
7: Adding c branch (c)
-------
abort: unknown revision 'z'
-------
=======
$ heads 0 1 2 3 4 5 6 7
7: Adding c branch (c)
6: Merging b branch head 2 and b branch head 3 (b)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
0: Adding root node ()
Topological heads:
$ heads -t
7: Adding c branch (c)
3: Adding b branch head 1 (b)
1: Adding a branch (a)
$ cd ..
______________
"created new head" message tests
$ hg init newheadmsg
$ cd newheadmsg
Init: no msg
$ echo 1 > a
$ hg ci -Am "a0: Initial root"
adding a
$ echo 2 >> a
$ hg ci -m "a1 (HN)"
$ hg branch b
marked working directory as branch b
(branches are permanent and global, did you want a bookmark?)
$ echo 1 > b
$ hg ci -Am "b2: Initial root for branch b"
adding b
$ echo 2 >> b
$ hg ci -m "b3 (HN)"
Case NN: msg
$ hg up -q null
$ hg branch -f b
marked working directory as branch b
$ echo 1 > bb
$ hg ci -Am "b4 (NN): new topo root for branch b"
adding bb
created new head
Case HN: no msg
$ echo 2 >> bb
$ hg ci -m "b5 (HN)"
Case BN: msg
$ hg branch -f default
marked working directory as branch default
$ echo 1 > aa
$ hg ci -Am "a6 (BN): new branch root"
adding aa
created new head
Case CN: msg
$ hg up -q 4
$ echo 3 >> bbb
$ hg ci -Am "b7 (CN): regular new head"
adding bbb
created new head
Case BB: msg
$ hg up -q 4
$ hg merge -q 3
$ hg branch -f default
marked working directory as branch default
$ hg ci -m "a8 (BB): weird new branch root"
created new head
Case CB: msg
$ hg up -q 4
$ hg merge -q 1
$ hg ci -m "b9 (CB): new head from branch merge"
created new head
Case HB: no msg
$ hg up -q 7
$ hg merge -q 6
$ hg ci -m "b10 (HB): continuing head from branch merge"
Case CC: msg
$ hg up -q 4
$ hg merge -q 2
$ hg ci -m "b11 (CC): new head from merge"
created new head
Case CH: no msg
$ hg up -q 2
$ hg merge -q 10
$ hg ci -m "b12 (CH): continuing head from merge"
Case HH: no msg
$ hg merge -q 3
$ hg ci -m "b12 (HH): merging two heads"
$ cd ..