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Version Control with Mercurial

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Exploring History

Overview

Teaching: 10 min
Exercises: 5 min
Questions

  • How do I review my changes?

  • How can I recover old versions of files?

Objectives

  • Compare files with older versions of themselves.

  • Display the changes that were made to files in a previous changeset.

If we want to see what we changed when, we use hg diff again, but refer to old versions using the --rev or -r flag and the revision numbers:

$ hg diff --rev 1:2 plan.txt

diff -r b31241913818 -r 2e15a7ee29c2 plan.txt
--- a/plan.txt  Tue Jun 09 15:16:11 2015 +0200
+++ b/plan.txt  Tue Jun 09 15:28:25 2015 +0200
@@ -1,3 +1,4 @@
 Goal: Run NEMO everyday to forecast storm surge water levels

 Need daily high resolution weather forcing from EC.
+Also need daily average Fraser River flow from EC.

$ hg diff -r 0:2 plan.txt

diff -r 1320339bbcae -r 2e15a7ee29c2 plan.txt
--- a/plan.txt  Tue Jun 09 14:41:27 2015 +0200
+++ b/plan.txt  Tue Jun 09 15:28:25 2015 +0200
@@ -1,1 +1,4 @@
 Goal: Run NEMO everyday to forecast storm surge water levels
+
+Need daily high resolution weather forcing from EC.
+Also need daily average Fraser River flow from EC.

In this way, we build up a chain of revisions. The most recent end of the chain is the changeset with the highest revision number.

To see what changes were made between a particular changeset and its parent use the --change or -c flag:

$ hg diff --change 1

diff -r 1320339bbcae -r b31241913818 plan.txt
--- a/plan.txt  Tue Jun 09 14:41:27 2015 +0200
+++ b/plan.txt  Tue Jun 09 15:16:11 2015 +0200
@@ -1,1 +1,3 @@
 Goal: Run NEMO everyday to forecast storm surge water levels
+
+Need daily high resolution weather forcing from EC.

Key Points

  • Use hg diff to compare different versions of files.

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