Add functions to support the merge implementation

Including commit distance, shortlog, and merge-base locator.

1 files changed, 84 insertions, 0 deletions

diff --git a/repo-access.sh b/repo-access.sh
index 6f6bf74..2b6a5cc 100644
--- a/repo-access.sh
+++ b/repo-access.sh
@@ -36,6 +36,90 @@ function systr_repo_resolve_reference
 }
 
 ##
+# systr_repo_commit_dist <a> <b>
+#
+# Determine how many commits have occurred between <a> and <b>.
+# IE:  How far behind <b> is <a>?  If <a> and <b> are (or
+# reference) the same commit, the result it zero.  Result
+# written to stdout.
+##
+function systr_repo_commit_dist
+{
+    if [ $# -lt 2 ]; then
+        echo "Fatal: too few args to repo_commit_dist" >&2
+        exit 1
+    fi
+
+    a=$(systr_repo_resolve_reference "$1")
+    b=$(systr_repo_resolve_reference "$2")
+    d=$((0))
+
+    while [[ "$b" != "NULL" ]]
+    do
+        if [[ "$b" == "$a" ]]; then
+            echo "$d"
+            exit
+        fi
+
+        d=$(($d+1))
+        read b <"$path/revs/$b/.commit.systr"
+    done
+
+    echo "Inf"
+}
+
+##
+# systrunk shortlog [<commit>=BASE]
+#
+# View commit history.  Generate list of commit IDs only, each
+# one a newline.  Written to stdout.
+##
+function systr_short_log
+{
+    if [ $# -lt 1 ]; then
+        commit="$BASE"
+    else
+        commit=$(systr_repo_resolve_reference "$1")
+    fi
+
+    while [[ "$commit" != "NULL" ]]
+    do
+        echo "$commit"
+        read commit <"$path/revs/$commit/.commit.systr"
+    done
+}
+
+##
+# systr_repo_merge_base <a> <b>
+#
+# Find the merge base between <a> and <b>.  That is, determine
+# which other commit is the closest common ancestor of both
+# <a> and <b>.  Result or "NULL" written to stdout.
+##
+function systr_repo_merge_base
+{
+    if [ $# -lt 2 ]; then
+        echo "Fatal: too few args to repo_merge_base" >&2
+        exit 1
+    fi
+
+    a=$(systr_repo_resolve_reference "$1")
+    b=$(systr_repo_resolve_reference "$2")
+
+    while [[ "$a" != "NULL" ]]
+    do
+        check=$(systr_short_log "$b" | grep "$a")
+
+        if [[ "$check" == "$a" ]]; then
+            echo "$a"
+            exit
+        fi
+
+        read a <"$path/revs/$a/.commit.systr"
+    done
+}
+
+##
 # systrunk log [<commit>=BASE]
 #
 # View commit history.  Generate a dump of all commits reachable