git-gui: Refactor branch switch to support detached head

[git/libgit-gsoc.git] / lib / checkout_op.tcl

# git-gui commit checkout support
# Copyright (C) 2007 Shawn Pearce

class checkout_op {

field w        {}; # our window (if we have one)
field w_cons   {}; # embedded console window object

field new_expr   ; # expression the user saw/thinks this is
field new_hash   ; # commit SHA-1 we are switching to
field new_ref    ; # ref we are updating/creating

field parent_w      .; # window that started us
field merge_type none; # type of merge to apply to existing branch
field fetch_spec   {}; # refetch tracking branch if used?
field checkout      1; # actually checkout the branch?
field create        0; # create the branch if it doesn't exist?

field reset_ok      0; # did the user agree to reset?
field fetch_ok      0; # did the fetch succeed?

field update_old   {}; # was the update-ref call deferred?
field reflog_msg   {}; # log message for the update-ref call

constructor new {expr hash {ref {}}} {
        set new_expr $expr
        set new_hash $hash
        set new_ref  $ref

        return $this
}

method parent {path} {
        set parent_w [winfo toplevel $path]
}

method enable_merge {type} {
        set merge_type $type
}

method enable_fetch {spec} {
        set fetch_spec $spec
}

method enable_checkout {co} {
        set checkout $co
}

method enable_create {co} {
        set create $co
}

method run {} {
        if {$fetch_spec ne {}} {
                global M1B

                # We were asked to refresh a single tracking branch
                # before we get to work.  We should do that before we
                # consider any ref updating.
                #
                set fetch_ok 0
                set l_trck [lindex $fetch_spec 0]
                set remote [lindex $fetch_spec 1]
                set r_head [lindex $fetch_spec 2]
                regsub ^refs/heads/ $r_head {} r_name

                _toplevel $this {Refreshing Tracking Branch}
                set w_cons [::console::embed \
                        $w.console \
                        "Fetching $r_name from $remote"]
                pack $w.console -fill both -expand 1
                $w_cons exec \
                        [list git fetch $remote +$r_head:$l_trck] \
                        [cb _finish_fetch]

                bind $w <$M1B-Key-w> break
                bind $w <$M1B-Key-W> break
                bind $w <Visibility> "
                        [list grab $w]
                        [list focus $w]
                "
                wm protocol $w WM_DELETE_WINDOW [cb _noop]
                tkwait window $w

                if {!$fetch_ok} {
                        delete_this
                        return 0
                }
        }

        if {$new_ref ne {}} {
                # If we have a ref we need to update it before we can
                # proceed with a checkout (if one was enabled).
                #
                if {![_update_ref $this]} {
                        delete_this
                        return 0
                }
        }

        if {$checkout} {
                _checkout $this
                return 1
        }

        delete_this
        return 1
}

method _noop {} {}

method _finish_fetch {ok} {
        if {$ok} {
                set l_trck [lindex $fetch_spec 0]
                if {[catch {set new_hash [git rev-parse --verify "$l_trck^0"]} err]} {
                        set ok 0
                        $w_cons insert "fatal: Cannot resolve $l_trck"
                        $w_cons insert $err
                }
        }

        $w_cons done $ok
        set w_cons {}
        wm protocol $w WM_DELETE_WINDOW {}

        if {$ok} {
                destroy $w
                set w {}
        } else {
                button $w.close -text Close -command [list destroy $w]
                pack $w.close -side bottom -anchor e -padx 10 -pady 10
        }

        set fetch_ok $ok
}

method _update_ref {} {
        global null_sha1 current_branch

        set ref $new_ref
        set new $new_hash

        set is_current 0
        set rh refs/heads/
        set rn [string length $rh]
        if {[string equal -length $rn $rh $ref]} {
                set newbranch [string range $ref $rn end]
                if {$current_branch eq $newbranch} {
                        set is_current 1
                }
        } else {
                set newbranch $ref
        }

        if {[catch {set cur [git rev-parse --verify "$ref^0"]}]} {
                # Assume it does not exist, and that is what the error was.
                #
                if {!$create} {
                        _error $this "Branch '$newbranch' does not exist."
                        return 0
                }

                set reflog_msg "branch: Created from $new_expr"
                set cur $null_sha1
        } elseif {$create && $merge_type eq {none}} {
                # We were told to create it, but not do a merge.
                # Bad.  Name shouldn't have existed.
                #
                _error $this "Branch '$newbranch' already exists."
                return 0
        } elseif {!$create && $merge_type eq {none}} {
                # We aren't creating, it exists and we don't merge.
                # We are probably just a simple branch switch.
                # Use whatever value we just read.
                #
                set new      $cur
                set new_hash $cur
        } elseif {$new eq $cur} {
                # No merge would be required, don't compute anything.
                #
        } else {
                set mrb {}
                catch {set mrb [git merge-base $new $cur]}
                switch -- $merge_type {
                ff {
                        if {$mrb eq $new} {
                                # The current branch is actually newer.
                                #
                                set new $cur
                        } elseif {$mrb eq $cur} {
                                # The current branch is older.
                                #
                                set reflog_msg "merge $new_expr: Fast-forward"
                        } else {
                                _error $this "Branch '$newbranch' already exists.\n\nIt cannot fast-forward to $new_expr.\nA merge is required."
                                return 0
                        }
                }
                reset {
                        if {$mrb eq $cur} {
                                # The current branch is older.
                                #
                                set reflog_msg "merge $new_expr: Fast-forward"
                        } else {
                                # The current branch will lose things.
                                #
                                if {[_confirm_reset $this $cur]} {
                                        set reflog_msg "reset $new_expr"
                                } else {
                                        return 0
                                }
                        }
                }
                default {
                        _error $this "Only 'ff' and 'reset' merge is currently supported."
                        return 0
                }
                }
        }

        if {$new ne $cur} {
                if {$is_current} {
                        # No so fast.  We should defer this in case
                        # we cannot update the working directory.
                        #
                        set update_old $cur
                        return 1
                }

                if {[catch {
                                git update-ref -m $reflog_msg $ref $new $cur
                        } err]} {
                        _error $this "Failed to update '$newbranch'.\n\n$err"
                        return 0
                }
        }

        return 1
}

method _checkout {} {
        if {[lock_index checkout_op]} {
                after idle [cb _start_checkout]
        } else {
                _error $this "Index is already locked."
                delete_this
        }
}

method _start_checkout {} {
        global HEAD commit_type

        # -- Our in memory state should match the repository.
        #
        repository_state curType curHEAD curMERGE_HEAD
        if {[string match amend* $commit_type]
                && $curType eq {normal}
                && $curHEAD eq $HEAD} {
        } elseif {$commit_type ne $curType || $HEAD ne $curHEAD} {
                info_popup {Last scanned state does not match repository state.

Another Git program has modified this repository since the last scan.  A rescan must be performed before the current branch can be changed.

The rescan will be automatically started now.
}
                unlock_index
                rescan ui_ready
                delete_this
                return
        }

        if {[is_config_true gui.trustmtime]} {
                _readtree $this
        } else {
                ui_status {Refreshing file status...}
                set cmd [list git update-index]
                lappend cmd -q
                lappend cmd --unmerged
                lappend cmd --ignore-missing
                lappend cmd --refresh
                set fd [open "| $cmd" r]
                fconfigure $fd -blocking 0 -translation binary
                fileevent $fd readable [cb _refresh_wait $fd]
        }
}

method _refresh_wait {fd} {
        read $fd
        if {[eof $fd]} {
                close $fd
                _readtree $this
        }
}

method _name {} {
        if {$new_ref eq {}} {
                return [string range $new_hash 0 7]
        }

        set rh refs/heads/
        set rn [string length $rh]
        if {[string equal -length $rn $rh $new_ref]} {
                return [string range $new_ref $rn end]
        } else {
                return $new_ref
        }
}

method _readtree {} {
        global HEAD

        ui_status "Updating working directory to '[_name $this]'..."
        set cmd [list git read-tree]
        lappend cmd -m
        lappend cmd -u
        lappend cmd --exclude-per-directory=.gitignore
        lappend cmd $HEAD
        lappend cmd $new_hash
        set fd [open "| $cmd" r]
        fconfigure $fd -blocking 0 -translation binary
        fileevent $fd readable [cb _readtree_wait $fd]
}

method _readtree_wait {fd} {
        global selected_commit_type commit_type HEAD MERGE_HEAD PARENT
        global current_branch is_detached
        global ui_comm

        # -- We never get interesting output on stdout; only stderr.
        #
        read $fd
        fconfigure $fd -blocking 1
        if {![eof $fd]} {
                fconfigure $fd -blocking 0
                return
        }

        set name [_name $this]

        # -- The working directory wasn't in sync with the index and
        #    we'd have to overwrite something to make the switch. A
        #    merge is required.
        #
        if {[catch {close $fd} err]} {
                regsub {^fatal: } $err {} err
                warn_popup "File level merge required.

$err

Staying on branch '$current_branch'."
                ui_status "Aborted checkout of '$name' (file level merging is required)."
                unlock_index
                delete_this
                return
        }

        set log "checkout: moving"
        if {!$is_detached} {
                append log " from $current_branch"
        }

        # -- Move/create HEAD as a symbolic ref.  Core git does not
        #    even check for failure here, it Just Works(tm).  If it
        #    doesn't we are in some really ugly state that is difficult
        #    to recover from within git-gui.
        #
        set rh refs/heads/
        set rn [string length $rh]
        if {[string equal -length $rn $rh $new_ref]} {
                set new_branch [string range $new_ref $rn end]
                append log " to $new_branch"

                if {[catch {
                                git symbolic-ref -m $log HEAD $new_ref
                        } err]} {
                        _fatal $this $err
                }
                set current_branch $new_branch
                set is_detached 0
        } else {
                append log " to $new_expr"

                if {[catch {
                                _detach_HEAD $log $new_hash
                        } err]} {
                        _fatal $this $err
                }
                set current_branch HEAD
                set is_detached 1
        }

        # -- We had to defer updating the branch itself until we
        #    knew the working directory would update.  So now we
        #    need to finish that work.  If it fails we're in big
        #    trouble.
        #
        if {$update_old ne {}} {
                if {[catch {
                                git update-ref \
                                        -m $reflog_msg \
                                        $new_ref \
                                        $new_hash \
                                        $update_old
                        } err]} {
                        _fatal $this $err
                }
        }

        if {$is_detached} {
                info_popup "You are no longer on a local branch.

If you wanted to be on a branch, create one now starting from 'This Detached Checkout'."
        }

        # -- Update our repository state.  If we were previously in
        #    amend mode we need to toss the current buffer and do a
        #    full rescan to update our file lists.  If we weren't in
        #    amend mode our file lists are accurate and we can avoid
        #    the rescan.
        #
        unlock_index
        set selected_commit_type new
        if {[string match amend* $commit_type]} {
                $ui_comm delete 0.0 end
                $ui_comm edit reset
                $ui_comm edit modified false
                rescan [list ui_status "Checked out '$name'."]
        } else {
                repository_state commit_type HEAD MERGE_HEAD
                set PARENT $HEAD
                ui_status "Checked out '$name'."
        }
        delete_this
}

git-version proc _detach_HEAD {log new} {
        >= 1.5.3 {
                git update-ref --no-deref -m $log HEAD $new
        }
        default {
                set p [gitdir HEAD]
                file delete $p
                set fd [open $p w]
                fconfigure $fd -translation lf -encoding utf-8
                puts $fd $new
                close $fd
        }
}

method _confirm_reset {cur} {
        set reset_ok 0
        set name [_name $this]
        set gitk [list do_gitk [list $cur ^$new_hash]]

        _toplevel $this {Confirm Branch Reset}
        pack [label $w.msg1 \
                -anchor w \
                -justify left \
                -text "Resetting '$name' to $new_expr will lose the following commits:" \
                ] -anchor w

        set list $w.list.l
        frame $w.list
        text $list \
                -font font_diff \
                -width 80 \
                -height 10 \
                -wrap none \
                -xscrollcommand [list $w.list.sbx set] \
                -yscrollcommand [list $w.list.sby set]
        scrollbar $w.list.sbx -orient h -command [list $list xview]
        scrollbar $w.list.sby -orient v -command [list $list yview]
        pack $w.list.sbx -fill x -side bottom
        pack $w.list.sby -fill y -side right
        pack $list -fill both -expand 1
        pack $w.list -fill both -expand 1 -padx 5 -pady 5

        pack [label $w.msg2 \
                -anchor w \
                -justify left \
                -text {Recovering lost commits may not be easy.} \
                ]
        pack [label $w.msg3 \
                -anchor w \
                -justify left \
                -text "Reset '$name'?" \
                ]

        frame $w.buttons
        button $w.buttons.visualize \
                -text Visualize \
                -command $gitk
        pack $w.buttons.visualize -side left
        button $w.buttons.reset \
                -text Reset \
                -command "
                        set @reset_ok 1
                        destroy $w
                "
        pack $w.buttons.reset -side right
        button $w.buttons.cancel \
                -default active \
                -text Cancel \
                -command [list destroy $w]
        pack $w.buttons.cancel -side right -padx 5
        pack $w.buttons -side bottom -fill x -pady 10 -padx 10

        set fd [open "| git rev-list --pretty=oneline $cur ^$new_hash" r]
        while {[gets $fd line] > 0} {
                set abbr [string range $line 0 7]
                set subj [string range $line 41 end]
                $list insert end "$abbr  $subj\n"
        }
        close $fd
        $list configure -state disabled

        bind $w    <Key-v> $gitk
        bind $w <Visibility> "
                grab $w
                focus $w.buttons.cancel
        "
        bind $w <Key-Return> [list destroy $w]
        bind $w <Key-Escape> [list destroy $w]
        tkwait window $w
        return $reset_ok
}

method _error {msg} {
        if {[winfo ismapped $parent_w]} {
                set p $parent_w
        } else {
                set p .
        }

        tk_messageBox \
                -icon error \
                -type ok \
                -title [wm title $p] \
                -parent $p \
                -message $msg
}

method _toplevel {title} {
        regsub -all {::} $this {__} w
        set w .$w

        if {[winfo ismapped $parent_w]} {
                set p $parent_w
        } else {
                set p .
        }

        toplevel $w
        wm title $w $title
        wm geometry $w "+[winfo rootx $p]+[winfo rooty $p]"
}

method _fatal {err} {
        error_popup "Failed to set current branch.

This working directory is only partially switched.  We successfully updated your files, but failed to update an internal Git file.

This should not have occurred.  [appname] will now close and give up.

$err"
        exit 1
}

}