test: make test-extdiff resilient to */gnubin/echo

My Mac test machine has 'echo' in '/opt/local/libexec/gnubin/echo' since, well,
GNU is not BSD.

Also, I feel it need to be said about using regexes:

Some people, when confronted with a problem, think "I know, I'll use regular
expressions." Now they have two problems.

tests/test-extdiff.t

@@ -1,340 +1,340 b''
   $ echo "[extensions]" >> $HGRCPATH
   $ echo "extdiff=" >> $HGRCPATH
 
   $ hg init a
   $ cd a
   $ echo a > a
   $ echo b > b
   $ hg add
   adding a
   adding b
 
 Should diff cloned directories:
 
   $ hg extdiff -o -r $opt
   Only in a: a
   Only in a: b
   [1]
 
   $ cat <<EOF >> $HGRCPATH
   > [extdiff]
   > cmd.falabala = echo
   > opts.falabala = diffing
   > cmd.edspace = echo
   > opts.edspace = "name  <[e-mail]>"
   > EOF
 
   $ hg falabala
   diffing a.000000000000 a
   [1]
 
   $ hg help falabala
   hg falabala [OPTION]... [FILE]...
   
   use 'echo' to diff repository (or selected files)
   
       Show differences between revisions for the specified files, using the
       'echo' program.
   
       When two revision arguments are given, then changes are shown between
       those revisions. If only one revision is specified then that revision is
       compared to the working directory, and, when no revisions are specified,
       the working directory files are compared to its parent.
   
   options ([+] can be repeated):
   
    -o --option OPT [+]      pass option to comparison program
    -r --rev REV [+]         revision
    -c --change REV          change made by revision
    -I --include PATTERN [+] include names matching the given patterns
    -X --exclude PATTERN [+] exclude names matching the given patterns
   
   (some details hidden, use --verbose to show complete help)
 
   $ hg ci -d '0 0' -mtest1
 
   $ echo b >> a
   $ hg ci -d '1 0' -mtest2
 
 Should diff cloned files directly:
 
   $ hg falabala -r 0:1
   diffing */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Test diff during merge:
 
   $ hg update -C 0
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ echo c >> c
   $ hg add c
   $ hg ci -m "new branch" -d '1 0'
   created new head
   $ hg merge 1
   1 files updated, 0 files merged, 0 files removed, 0 files unresolved
   (branch merge, don't forget to commit)
 
 Should diff cloned file against wc file:
 
   $ hg falabala
   diffing */extdiff.*/a.2a13a4d2da36/a */a/a (glob)
   [1]
 
 
 Test --change option:
 
   $ hg ci -d '2 0' -mtest3
   $ hg falabala -c 1
   diffing */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Check diff are made from the first parent:
 
   $ hg falabala -c 3 || echo "diff-like tools yield a non-zero exit code"
   diffing */extdiff.*/a.2a13a4d2da36/a a.46c0e4daeb72/a (glob)
   diff-like tools yield a non-zero exit code
 
 issue4463: usage of command line configuration without additional quoting
 
   $ cat <<EOF >> $HGRCPATH
   > [extdiff]
   > cmd.4463a = echo
   > opts.4463a = a-naked 'single quoted' "double quoted"
   > 4463b = echo b-naked 'single quoted' "double quoted"
   > echo =
   > EOF
   $ hg update -q -C 0
   $ echo a >> a
 #if windows
   $ hg --debug 4463a | grep '^running'
   running 'echo a-naked \'single quoted\' "double quoted" *\\a *\\a' in */extdiff.* (glob)
   $ hg --debug 4463b | grep '^running'
   running 'echo b-naked \'single quoted\' "double quoted" *\\a *\\a' in */extdiff.* (glob)
   $ hg --debug echo | grep '^running'
   running '*echo* *\\a *\\a' in */extdiff.* (glob)
 #else
   $ hg --debug 4463a | grep '^running'
   running 'echo a-naked \'single quoted\' "double quoted" */a $TESTTMP/a/a' in */extdiff.* (glob)
   $ hg --debug 4463b | grep '^running'
   running 'echo b-naked \'single quoted\' "double quoted" */a $TESTTMP/a/a' in */extdiff.* (glob)
   $ hg --debug echo | grep '^running'
   running '*echo */a $TESTTMP/a/a' in */extdiff.* (glob)
 #endif
 
 (getting options from other than extdiff section)
 
   $ cat <<EOF >> $HGRCPATH
   > [extdiff]
   > # using diff-tools diffargs
   > 4463b2 = echo
   > # using merge-tools diffargs
   > 4463b3 = echo
   > # no diffargs
   > 4463b4 = echo
   > [diff-tools]
   > 4463b2.diffargs = b2-naked 'single quoted' "double quoted"
   > [merge-tools]
   > 4463b3.diffargs = b3-naked 'single quoted' "double quoted"
   > EOF
 #if windows
   $ hg --debug 4463b2 | grep '^running'
   running 'echo b2-naked \'single quoted\' "double quoted" *\\a *\\a' in */extdiff.* (glob)
   $ hg --debug 4463b3 | grep '^running'
   running 'echo b3-naked \'single quoted\' "double quoted" *\\a *\\a' in */extdiff.* (glob)
   $ hg --debug 4463b4 | grep '^running'
   running 'echo *\\a *\\a' in */extdiff.* (glob)
   $ hg --debug 4463b4 --option b4-naked --option 'being quoted' | grep '^running'
   running 'echo b4-naked "being quoted" *\\a *\\a' in */extdiff.* (glob)
   $ hg --debug extdiff -p echo --option echo-naked --option 'being quoted' | grep '^running'
   running 'echo echo-naked "being quoted" *\\a *\\a' in */extdiff.* (glob)
 #else
   $ hg --debug 4463b2 | grep '^running'
   running 'echo b2-naked \'single quoted\' "double quoted" */a $TESTTMP/a/a' in */extdiff.* (glob)
   $ hg --debug 4463b3 | grep '^running'
   running 'echo b3-naked \'single quoted\' "double quoted" */a $TESTTMP/a/a' in */extdiff.* (glob)
   $ hg --debug 4463b4 | grep '^running'
   running 'echo */a $TESTTMP/a/a' in */extdiff.* (glob)
   $ hg --debug 4463b4 --option b4-naked --option 'being quoted' | grep '^running'
   running "echo b4-naked 'being quoted' */a $TESTTMP/a/a" in */extdiff.* (glob)
   $ hg --debug extdiff -p echo --option echo-naked --option 'being quoted' | grep '^running'
   running "echo echo-naked 'being quoted' */a $TESTTMP/a/a" in */extdiff.* (glob)
 #endif
 
   $ touch 'sp ace'
   $ hg add 'sp ace'
   $ hg ci -m 'sp ace'
   created new head
   $ echo > 'sp ace'
 
 Test pre-72a89cf86fcd backward compatibility with half-baked manual quoting
 
   $ cat <<EOF >> $HGRCPATH
   > [extdiff]
   > odd =
   > [merge-tools]
   > odd.diffargs = --foo='\$clabel' '\$clabel' "--bar=\$clabel" "\$clabel"
   > odd.executable = echo
   > EOF
 #if windows
 TODO
 #else
   $ hg --debug odd | grep '^running'
-  running "*/bin/echo --foo='sp ace' 'sp ace' --bar='sp ace' 'sp ace'" in * (glob)
+  running "*/echo --foo='sp ace' 'sp ace' --bar='sp ace' 'sp ace'" in * (glob)
 #endif
 
 Empty argument must be quoted
 
   $ cat <<EOF >> $HGRCPATH
   > [extdiff]
   > kdiff3 = echo
   > [merge-tools]
   > kdiff3.diffargs=--L1 \$plabel1 --L2 \$clabel \$parent \$child
   > EOF
 #if windows
   $ hg --debug kdiff3 -r0 | grep '^running'
   running 'echo --L1 "@0" --L2 "" a.8a5febb7f867 a' in * (glob)
 #else
   $ hg --debug kdiff3 -r0 | grep '^running'
   running "echo --L1 '@0' --L2 '' a.8a5febb7f867 a" in * (glob)
 #endif
 
 #if execbit
 
 Test extdiff of multiple files in tmp dir:
 
   $ hg update -C 0 > /dev/null
   $ echo changed > a
   $ echo changed > b
   $ chmod +x b
 
 Diff in working directory, before:
 
   $ hg diff --git
   diff --git a/a b/a
   --- a/a
   +++ b/a
   @@ -1,1 +1,1 @@
   -a
   +changed
   diff --git a/b b/b
   old mode 100644
   new mode 100755
   --- a/b
   +++ b/b
   @@ -1,1 +1,1 @@
   -b
   +changed
 
 
 Edit with extdiff -p:
 
 Prepare custom diff/edit tool:
 
   $ cat > 'diff tool.py' << EOT
   > #!/usr/bin/env python
   > import time
   > time.sleep(1) # avoid unchanged-timestamp problems
   > file('a/a', 'ab').write('edited\n')
   > file('a/b', 'ab').write('edited\n')
   > EOT
 
   $ chmod +x 'diff tool.py'
 
 will change to /tmp/extdiff.TMP and populate directories a.TMP and a
 and start tool
 
   $ hg extdiff -p "`pwd`/diff tool.py"
   [1]
 
 Diff in working directory, after:
 
   $ hg diff --git
   diff --git a/a b/a
   --- a/a
   +++ b/a
   @@ -1,1 +1,2 @@
   -a
   +changed
   +edited
   diff --git a/b b/b
   old mode 100644
   new mode 100755
   --- a/b
   +++ b/b
   @@ -1,1 +1,2 @@
   -b
   +changed
   +edited
 
 Test extdiff with --option:
 
   $ hg extdiff -p echo -o this -c 1
   this */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
   $ hg falabala -o this -c 1
   diffing this */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Test extdiff's handling of options with spaces in them:
 
   $ hg edspace -c 1
   name  <[e-mail]> */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
   $ hg extdiff -p echo -o "name  <[e-mail]>" -c 1
   name  <[e-mail]> */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Test with revsets:
 
   $ hg extdif -p echo -c "rev(1)"
   */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
   $ hg extdif -p echo -r "0::1"
   */extdiff.*/a.8a5febb7f867/a a.34eed99112ab/a (glob)
   [1]
 
 Fallback to merge-tools.tool.executable|regkey
   $ mkdir dir
   $ cat > 'dir/tool.sh' << EOF
   > #!/bin/sh
   > echo "** custom diff **"
   > EOF
   $ chmod +x dir/tool.sh
   $ tool=`pwd`/dir/tool.sh
   $ hg --debug tl --config extdiff.tl= --config merge-tools.tl.executable=$tool
   making snapshot of 2 files from rev * (glob)
     a
     b
   making snapshot of 2 files from working directory
     a
     b
   running '$TESTTMP/a/dir/tool.sh a.* a' in */extdiff.* (glob)
   ** custom diff **
   cleaning up temp directory
   [1]
 
   $ cd ..
 
 #endif
 
 #if symlink
 
 Test symlinks handling (issue1909)
 
   $ hg init testsymlinks
   $ cd testsymlinks
   $ echo a > a
   $ hg ci -Am adda
   adding a
   $ echo a >> a
   $ ln -s missing linka
   $ hg add linka
   $ hg falabala -r 0 --traceback
   diffing testsymlinks.07f494440405 testsymlinks
   [1]
   $ cd ..
 
 #endif