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1 *usr_32.txt* For Vim version 7.2. Last change: 2006 Apr 30
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3 VIM USER MANUAL - by Bram Moolenaar
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4
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5 The undo tree
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6
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7
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8 Vim provides multi-level undo. If you undo a few changes and then make a new
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9 change you create a branch in the undo tree. This text is about moving
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10 through the branches.
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11
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12 |32.1| Numbering changes
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13 |32.2| Jumping around the tree
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14 |32.3| Time travelling
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15
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16 Next chapter: |usr_40.txt| Make new commands
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17 Previous chapter: |usr_31.txt| Exploiting the GUI
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18 Table of contents: |usr_toc.txt|
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19
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20 ==============================================================================
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21 *32.1* Numbering changes
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22
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23 In section |02.5| we only discussed one line of undo/redo. But it is also
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24 possible to branch off. This happens when you undo a few changes and then
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25 make a new change. The new changes become a branch in the undo tree.
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26
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27 Let's start with the text "one". The first change to make is to append
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28 " too". And then move to the first 'o' and change it into 'w'. We then have
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29 two changes, numbered 1 and 2, and three states of the text:
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30
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31 one ~
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32 |
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33 change 1
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34 |
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35 one too ~
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36 |
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37 change 2
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38 |
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39 one two ~
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40
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41 If we now undo one change, back to "one too", and change "one" to "me" we
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42 create a branch in the undo tree:
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43
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44 one ~
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45 |
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46 change 1
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47 |
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48 one too ~
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49 / \
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50 change 2 change 3
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51 | |
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52 one two me too ~
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53
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54 You can now use the |u| command to undo. If you do this twice you get to
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55 "one". Use |CTRL-R| to redo, and you will go to "one too". One more |CTRL-R|
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56 takes you to "me too". Thus undo and redo go up and down in the tree, using
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57 the branch that was last used.
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58
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59 What matters here is the order in which the changes are made. Undo and redo
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60 are not considered changes in this context. After each change you have a new
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61 state of the text.
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62
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63 Note that only the changes are numbered, the text shown in the tree above has
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64 no identifier. They are mostly referred to by the number of the change above
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65 it. But sometimes by the number of one of the changes below it, especially
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66 when moving up in the tree, so that you know which change was just undone.
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67
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68 ==============================================================================
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69 *32.2* Jumping around the tree
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70
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71 So how do you get to "one two" now? You can use this command: >
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72
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73 :undo 2
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74
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75 The text is now "one two", you are below change 2. You can use the |:undo|
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76 command to jump to below any change in the tree.
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77
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78 Now make another change: change "one" to "not":
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79
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80 one ~
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81 |
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82 change 1
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83 |
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84 one too ~
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85 / \
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86 change 2 change 3
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87 | |
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88 one two me too ~
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89 |
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90 change 4
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91 |
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92 not two ~
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93
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94 Now you change your mind and want to go back to "me too". Use the |g-|
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95 command. This moves back in time. Thus it doesn't walk the tree upwards or
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96 downwards, but goes to the change made before.
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97
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98 You can repeat |g-| and you will see the text change:
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99 me too ~
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100 one two ~
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101 one too ~
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102 one ~
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103
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104 Use |g+| to move forward in time:
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105 one ~
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106 one too ~
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107 one two ~
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108 me too ~
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109 not two ~
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110
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111 Using |:undo| is useful if you know what change you want to jump to. |g-| and
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112 |g+| are useful if you don't know exactly what the change number is.
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113
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114 You can type a count before |g-| and |g+| to repeat them.
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115
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116 ==============================================================================
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117 *32.3* Time travelling
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118
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119 When you have been working on text for a while the tree grows to become big.
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120 Then you may want to go to the text of some minutes ago.
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121
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122 To see what branches there are in the undo tree use this command: >
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123
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124 :undolist
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125 < number changes time ~
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126 3 2 16 seconds ago
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127 4 3 5 seconds ago
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128
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129 Here you can see the number of the leaves in each branch and when the change
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130 was made. Assuming we are below change 4, at "not two", you can go back ten
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131 seconds with this command: >
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132
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133 :earlier 10s
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134
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135 Depending on how much time you took for the changes you end up at a certain
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136 position in the tree. The |:earlier| command argument can be "m" for minutes
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137 and "h" for hours. To go all the way back use a big number: >
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138
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139 :earlier 10h
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140
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141 To travel forward in time again use the |:later| command: >
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142
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143 :later 1m
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144
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145 The arguments are "s", "m" and "h", just like with |:earlier|.
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146
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147 ==============================================================================
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148
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149 Next chapter: |usr_40.txt| Make new commands
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150
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151 Copyright: see |manual-copyright| vim:tw=78:ts=8:ft=help:norl:
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